Deblocking filter for sub-partition boundaries caused by intra sub-partition coding tool

ABSTRACT

It is provided a deblocking method, for deblocking a sub-partitions boundary within a coding block in image encoding and/or image decoding. The current coding block is coded in an intra prediction mode and the current coding block is partitioned into sub-partitions comprising a first sub-partition and a second sub-partition which is adjacent to the first sub-partition. The method comprises: determining a maximum filter length to be 1 for a first/second sub-partition when a width of the first or second sub-partition is 4 samples, or when a height of the first or second sub-partition is 4 samples; modifying a value of up to one sample of the first or second sub-partition, wherein the up to one sample is obtained from a row or a column of the first or second sub-partition that is perpendicular to and adjacent to the sub-partitions boundary between the first sub-partition and the second sub-partition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2020/071272, filed on Jan. 10, 2020, which claims the priority toU.S. Provisional Patent Application No. 62/791,003, filed on Jan. 10,2019. The disclosures of the aforementioned patent applications arehereby incorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field ofpicture processing and more particularly to deblocking filter forsub-partition boundaries caused by an intra sub-partition (ISP) codingtool.

BACKGROUND

Video coding (video encoding and decoding) is used in a wide range ofdigital video applications, for example broadcast digital TV, videotransmission over internet and mobile networks, real-time conversationalapplications such as video chat, video conferencing, DVD and Blu-raydiscs, video content acquisition and editing systems, and camcorders ofsecurity applications.

The amount of video data needed to depict even a relatively short videocan be substantial, which may result in difficulties when the data is tobe streamed or otherwise communicated across a communications networkwith limited bandwidth capacity. Thus, video data is generallycompressed before being communicated across modern daytelecommunications networks. The size of a video could also be an issuewhen the video is stored on a storage device because memory resourcesmay be limited. Video compression devices often use software and/orhardware at the source to code the video data prior to transmission orstorage, thereby decreasing the quantity of data needed to representdigital video images. The compressed data is then received at thedestination by a video decompression device that decodes the video data.With limited network resources and ever increasing demands of highervideo quality, improved compression and decompression techniques thatimprove compression ratio with little to no sacrifice in picture qualityare desirable.

Particularly, in the context of intra prediction an Intra Sub-Partition(ISP) coding tool was recently introduced in which an image block (suchas a transform unit (TU), a prediction unit (PU), a coding unit (CU)) ispartitioned into multiple sub-partitions. Intra sub-partition (ISP),however, may cause discontinuities in sample values across thesub-partition boundaries thereby causing undesirable boundary or edgeartifacts that are perceptible by a viewer. A goal in block-based imagecoding is to reduce edge artifacts below a visibility threshold. This isdone by performing deblocking filtering. Such a deblocking filtering ison the one hand performed on decoding side in order to remove thevisible edge artifacts, but also on encoding side, in order to preventthe edge artifacts from being encoded into the image at all.

Thus, there is a need for an improved in-loop deblocking filterapparatus and method providing efficient removal of blocking artifactsthat would be caused by an intra sub-partition coding tool.

SUMMARY

In view of the above-mentioned challenges, embodiments of the presentapplication aim to provide a deblocking filter apparatus, an encoder, adecoder and corresponding methods that may mitigate or even removeblocking artifacts that would be caused by an intra sub-partition codingtool, so as to improve coding efficiency.

Embodiments of the invention are defined by the features of theindependent claims, and further advantageous implementations of theembodiments by the features of the dependent claims.

Particular embodiments are outlined in the attached independent claims,with other embodiments in the dependent claims.

The foregoing and other objects are achieved by the subject matter ofthe independent claims. Further implementation forms are apparent fromthe dependent claims, the description and the figures.

According to a first aspect of the present disclosure, it is provided adeblocking method, for deblocking sub-partitions boundary within acoding block in an image encoding and/or an image decoding, wherein thecurrent coding block is coded in an intra prediction mode and thecurrent coding block is partitioned into sub-partitions comprising afirst sub-partition and a second sub-partition which is adjacent to thefirst sub-partition (such as the second sub-partition is on the right orbottom block of the first sub-partitions). In an example, the secondsub-partition is intra predicted based on the first sub-partition (i.e.the current coding block is coded using an Intra sub-partition, ISP,tool or the sub-partitions boundary is caused by an Intra sub-partition,ISP, tool, particularly the current coding block is partitioned intosub-partitions by the ISP coding tool and the sub-partitions inside areintra predicted one by one, such as from left to right or from top tobottom); wherein the method comprises:

determining a first maximum filter length to be 1 for the firstsub-partition and/or a second maximum filter length to be 1 for thesecond sub-partition when a width of the first sub-partition is 4samples or a width of the second sub-partition is 4 samples, or when aheight of the first sub-partition is 4 samples or a height of the secondsub-partition is 4 samples;

modifying (i.e. filtering) a value of up to one sample of the firstsub-partition, wherein the up to one sample is obtained from a row orcolumn of the first sub-partition that is perpendicular to and adjacentto the sub-partitions boundary between the first sub-partition and thesecond sub-partition; and/or

modifying (i.e. filtering) a value of up to one sample of the secondsub-partition, wherein the up to one sample is obtained from a row orcolumn of the second sub-partition that is perpendicular to and adjacentto the sub-partitions boundary between the first sub-partition and thesecond sub-partition.

It can be understood that the first maximum filter length for the firstsub-partition, may refer to in each row or column perpendicular to andadjacent to the sub-partitions boundary, a maximum number of samplesallowed to be modified for the first sub-partition. The second maximumfilter length for the second sub-partition, may refer to in each row orcolumn perpendicular to and adjacent to the sub-partitions boundary, amaximum number of samples allowed to be modified for the secondsub-partition. It can be understood that, depending on the particularfiltering decision phase, in some cases, no sample may be modified, orin other cases, only one sample may be modified in each row or columnperpendicular to and adjacent to the sub-partitions boundary.

Embodiments of the invention apply to both vertical and horizontalsub-partitions boundary. For vertical sub-partitions boundary, the widthof the first or second sub-partition is checked whether the width is 4samples. For horizontal sub-partitions boundary, the height of the firstor second sub-partition is checked whether the height is 4 samples.

It is noted that the term “block”, “coding block” or “image block” isused in the present disclosure which can be applied for prediction units(PUs), coding units (CUs), etc. In VVC in general transform units andcoding units are mostly aligned except in few scenarios when TU tilingor sub block transform (SBT) or ISP is used. It can be understood thatthe terms “block/image block/coding block” may be exchanged with eachother in the present disclosure. The terms “sample/pixel” may beexchanged with each other in the present disclosure.

The intra sub-partition coding tool partitions an intra prediction block(i.e. an intra coding block short for a current coding block which iscoded in intra prediction mode) into sub-partitions and predicts thesub-partitions inside one by one. There might be a discontinuity acrossthe sub-partition boundary. An improved filtering process is proposed toreduce the artifact caused by these sub-partition boundaries, in whichfiltering up to one sample is performed in the first or secondsub-partition when a height of the first or second sub-partition is 4samples or when a width of the first or second sub-partition is 4samples. This allows for modifying a small number of sample values atthe sub-partitions boundary, and therefore the method can reduce theblock artifacts that might be caused by sub-partition boundaries in thecurrent coding block due to the application of the ISP. The weakfiltering is advantageous in terms of the computational load.

In a possible implementation form of the method according to the firstaspect as such, wherein the up to one sample, which is obtained from thecolumn of the first or second sub-partition that is perpendicular to andadjacent to the boundary between the first and second sub-partitions, ismodified when a height of the first or second sub-partition is 4 samplesif an intra sub-partitions split type of partitioning the current codingblock into sub-partitions is horizontal. It can be understood that “theup to one sample is modified” may refer to at most one sample is allowedto be modified. That is, depending on the particular filtering decisionphase, in some cases, no sample may be modified, or in other cases, onlyone sample may be modified in each column perpendicular to and adjacentto the sub-partitions boundary.

In a possible implementation form of the method according to the firstaspect as such, wherein the up to one sample, which is obtained from therow of the first or second sub-partition that is perpendicular to andadjacent to the boundary between the first and second sub-partitions, ismodified when a width of the first or second sub-partition is 4 samplesif an intra sub-partitions split type of partitioning the current codingblock into sub-partitions is vertical. It can be understood that “the upto one sample is modified” may refer to at most one sample is allowed tobe modified. That is, depend on the particular filtering decision phase,in some cases, no sample may be modified, or in other cases only onesample may be modified in each row perpendicular to and adjacent to thesub-partitions boundary.

In a possible implementation form of the method according to anypreceding implementation of the first aspect or the first aspect assuch, wherein if the intra sub-partitions split type of partitioning thecurrent coding block into sub-partitions is horizontal, thesub-partitions boundary between the first and second sub-partitions is ahorizontal sub-partitions boundary; Alternatively, if the intrasub-partitions split type of partitioning the current coding block intosub-partitions is vertical, the sub-partitions boundary between thefirst and second sub-partitions is a vertical sub-partitions boundary.

In a possible implementation form of the method according to anypreceding implementation of the first aspect or the first aspect assuch, wherein if the intra sub-partitions split type of partitioning thecurrent coding block into sub-partitions is vertical, the firstsub-partition may be left to the second sub-partition and the secondsub-partition may be intra predicted based on a reconstructed value(e.g. a reconstructed version) of the first sub-partition;

if the intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is horizontal, the first sub-partitionmay be top of the second sub-partition and the second sub-partition maybe intra predicted based on a reconstructed value (e.g. a reconstructedversion) of the first sub-partition.

It can be understood that, the second sub-partition is intra predictedbased on the reconstructed version (i.e. reconstructed values) of thefirst sub-partition. The reconstructed first sub-partition represents areference for intra prediction of the second sub-partition. It is notedthat after a current picture to which the current coding block belongsare reconstructed, the reconstructed picture is input to the filteringprocess. During the reconstruction of the current picture, the currentcoding block which is applied by the ISP coding tool is intra predictedto obtain the predictive block (e.g. predicted values) of the currentcoding block, in particular, the sub-partitions inside the current intracoding block are intra predicted one by one.

In a possible implementation form of the method according to anypreceding implementation of the first aspect or the first aspect assuch, wherein the number of sub-partitions is 2 or 4.

In a possible implementation form of the method according to anypreceding implementation of the first aspect or the first aspect assuch, wherein

if a width of the current coding block is equal to 4 and a height of thecoding block is equal to 8 and/or if the width of the current codingblock is equal to 8 and the height of the current coding block is equalto 4, the number of sub-partitions is 2,

otherwise, the number of sub-partitions is 4.

In a possible implementation form of the method according to anypreceding implementation of the first aspect or the first aspect assuch, wherein the up to one sample in the first or second sub-partitionis modified even if the sub-partitions boundary between the first andsecond sub-partitions is not overlapped with an n×n sample grid, whereinn is an integer.

It is allowed to de-blocking the target boundaries, which is not alignedwith an n×n grid, but is caused by ISP and is an internal boundarybetween sub-partitions of a coding block.

In a possible implementation form of the method according to anypreceding implementation of the first aspect or the first aspect assuch, wherein the up to one sample in the first or second sub-partitionis modified only if the sub-partitions boundary between the first andsecond sub-partitions overlaps with an n×n sample grid, wherein n is aninteger, for example, n=4 or n=8. Thereby, the computational load may befurther reduced.

Moreover, the filtering of up to one sample in the sub-partitions may beperformed only when the heights of all of the sub-partitions are 4samples or when the widths of all of the sub-partitions are 4 samples.Thereby, the computational load of the overall coding process may befurther reduced.

In general, the sub-partitions may be rectangular transform blocksub-partitions.

In a possible implementation form of the method according to anypreceding implementation of the first aspect or the first aspect assuch, wherein samples of the sub-partitions are luma samples, or thesamples of the sub-partitions are chroma samples.

In a possible implementation form of the method according to anypreceding implementation of the first aspect or the first aspect assuch, the order of intra predicting the sub-partitions is from left toright if the intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is vertical or wherein the order ofintra predicting the sub-partitions is from top to down if the intrasub-partitions split type of partitioning the current coding block intosub-partitions is horizontal. That is, the partitioning of theprediction block into the sub-partitions may be performed in a verticaldirection. In this case, the order of intra predicting thesub-partitions is one by one from left to right. Alternatively, thepartitioning of the prediction block into the sub-partitions may beperformed in a horizontal direction. In this case, the order of intrapredicting the two sub-partitions is one by one from top to down.

In the present disclosure, the current coding block is coded using anintra sub-partition (ISP) tool or the sub-partitions boundary is causedby an intra sub-partition (ISP) tool.

In general, boundary strengths of all boundaries between thesub-partitions of the coding block may be set to a constant valueindicating the strength of the filtering process (for example, 2) inorder to simplify the overall processing.

Moreover, in the above-described embodiments, the method may compriseobtaining coded block flag, CBF, values corresponding to two adjacentsub-partitions, determining a boundary strength of a boundary betweentwo adjacent sub-partitions of the current block, according to the CBFvalues corresponding to the two adjacent sub-partitions and

performing the filtering decision whether filtering is performed or notaccording to the determined boundary strength. At least one of the CBFvalues corresponding to two adjacent sub-partitions may be not equal to0, where 0 implies that there is no residual data after quantization ofthat sub-partition.

According to a second aspect of the present disclosure, it is provided ade-blocking method, for deblocking block edges between image blocks inan image encoding and/or an image decoding, wherein the block edgescomprises an edge between a current sub-partition of a current codingblock (i.e. a current intra coding block) and a neighboring block of thecurrent coding block, wherein the current coding block is coded in intraprediction mode and the current coding block is partitioned intosub-partitions (or the current coding block is coded using an Intrasub-partition, ISP, tool or sub-partitions is caused by an Intrasub-partition, ISP, tool); wherein the method comprises:

determining a third maximum filter length to be 1 for the currentsub-partition and/or a fourth maximum filter length to be 1 for theneighboring block when a width of the current sub-partition is 4 samplesor a height of the current sub-partition is 4 samples;

modifying a value of up to one sample of the current sub-partition,wherein the up to one sample is obtained from a row or column of thecurrent sub-partition that is perpendicular to and adjacent to the edgebetween the current sub-partition and the neighboring block; and/or

modifying a value of up to one sample of the neighboring block, whereinthe up to one sample is obtained from a row or column of the neighboringblock that is perpendicular to and adjacent to the edge between thecurrent sub-partition and the neighboring block.

It is noted that if the number of sub-partitions is two, the currentsub-partition may be the first sub-partition or the second sub-partitionaccording to the first aspect as such. If the number of sub-partitionsis more than two, such as four, the current sub-partition may be theleftmost sub-partition or the rightmost sub-partition inside the currentcoding block if an intra sub-partitions split type of partitioning thecurrent coding block into sub-partitions is vertical, or the currentsub-partition may be the topmost sub-partition or the lowermostsub-partition inside the current coding block if an intra sub-partitionssplit type of partitioning the current coding block into sub-partitionsis horizontal.

In the second aspect of the present disclosure, the currentsub-partition is intra predicted based on the neighboring block which isadjacent from top or left. It is noted that the neighboring block mightnot be a coding block with further partitions, i.e. there probably willno sub-partition of the neighboring block.

It can be understood that the third maximum filter length for thecurrent sub-partition, may refer to in each row or column perpendicularto and adjacent to the edge, a maximum number of samples allowed to bemodified for the current sub-partition. The fourth maximum filter lengthfor the neighboring block, may refer to in each row or columnperpendicular to and adjacent to the edge, a maximum number of samplesallowed to be modified for the neighboring block. It can be understoodthat, depend on the particular filtering decision phase, in some cases,no sample may be modified, or in other cases, only one sample may bemodified in each row or column perpendicular to and adjacent to thesub-partitions boundary.

Embodiments of the invention apply to both vertical and horizontal edgebetween the current sub-partition and the neighboring block. Forvertical edge, the width of the current sub-partition or the neighboringblock is checked whether the width is 4 samples. For a horizontal edge,the height of the current sub-partition or neighboring block is checkedwhether the height is 4 samples.

The difference between block edge and sub-partitions boundary isdescribed in the further description. A sub-partitions boundary is anedge which is internal to a coding block which uses Intra sub-partition(ISP) coding tools, and a block edge (i.e. a coding unit (CU) edge or acoding block edge or CU boundary) is an edge shared between two codingunits or two coding blocks.

The intra sub-partition coding tool partitions an intra prediction block(i.e. an intra coding block, short for a current coding block which iscoded in intra prediction mode) into sub-partitions and predicts thesub-partitions inside the intra prediction block one by one. There mightbe a discontinuity across the edge between the current sub-partition ofthe current coding block and a neighboring block of the current codingblock. Therefore, an improved filtering process is proposed to reducethe artifact caused by such an edge, in which filtering up to one samplein a current sub-partition or the neighboring block when a height of thecurrent sub-partition is 4 samples or a width of the currentsub-partition is 4 samples. This allows for modifying a small number ofsample values at the edge, and therefore the method can reduce the blockartifacts that might be caused by the edge between the current block towhich the ISP is applied and the neighboring block while avoidingfiltering overlaps between the edge and a sub-partitions boundary to acertain extent.

In a possible implementation form of the method according to the secondaspect as such,

wherein the up to one sample, which is obtained from the column of thecurrent sub-partition that is perpendicular to and adjacent to the edgebetween the current sub-partition and the neighboring block that isbelow or top of the current sub-partition, is modified when a height ofthe current sub-partition is 4 samples if an intra sub-partitions splittype of partitioning the current coding block into sub-partitions ishorizontal. It can be understood that, “the up to one sample ismodified” may refer to at most one sample is allowed to be modified.That is, depending on the particular filtering decision phase, in somecases no sample may be modified, or in other cases only one sample maybe modified in each column perpendicular to and adjacent to the edge.

In a possible implementation form of the method according to the secondaspect as such,

wherein the up to one sample, which is obtained from the row of thecurrent sub-partition that is perpendicular to and adjacent to the edgebetween the current sub-partition and the neighboring block that is leftor right to the current sub-partition, is modified when a width of thecurrent sub-partition is 4 samples if an intra sub-partitions split typeof partitioning the current coding block into sub-partitions isvertical. It can be understood that, “the up to one sample is modified”may refer to at most one sample is allowed to be modified. That is,depending on the particular filtering decision phase, in some cases nosample may be modified, or in other cases only one sample may bemodified in each row perpendicular to and adjacent to the edge.

In a possible implementation form of the method according to anypreceding implementation of the second aspect or the second aspect assuch, wherein if the intra sub-partitions split type of partitioning thecurrent coding block into sub-partitions is vertical, the currentsub-partition is right to the neighboring block and the currentsub-partition is intra predicted based on a reconstructed value of theneighboring block;

if the intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is horizontal, the currentsub-partition is bottom of the neighboring block and the currentsub-partition is intra predicted based on a reconstructed value of theneighboring block.

The current sub-partition may be intra predicted based on another codingblock that is positioned adjacent to the coding block. This other codingblock may be top of the coding block or left of the coding block. To bemore precise, the current sub-partition may be intra predicted based onthe reconstructed version of the neighboring coding block.

In a possible implementation form of the method according to anypreceding implementation of the second aspect or the second aspect assuch, wherein the number of sub-partitions is 2 or 4.

In a possible implementation form of the method according to anypreceding implementation of the second aspect or the second aspect assuch, wherein

if a width of the current coding block is equal to 4 and a height of thecoding block is equal to 8 and/or if the width of the current codingblock is equal to 8 and the height of the current coding block is equalto 4, the number of sub-partitions is 2,

otherwise, the number of sub-partitions is 4.

In a possible implementation form of the method according to anypreceding implementation of the second aspect or the second aspect assuch, wherein the up to one sample in the current sub-partition or inthe neighboring block is modified even if the edge between the currentsub-partition and the neighboring block is not overlapped with an n×nsample grid, wherein n is an integer. For example, n=4 or n=8.

In a possible implementation form of the method according to anypreceding implementation of the second aspect or the second aspect assuch, wherein the up to one sample in the current sub-partition or inthe neighboring block only if the edge between the current sub-partitionand the neighboring block overlaps with an n×n sample grid, wherein n isan integer. For example, n=4 or n=8.

In a possible implementation form of the method according to anypreceding implementation of the second aspect or the second aspect assuch, wherein samples of the sub-partitions are luma samples, or thesamples of the sub-partitions are chroma samples.

In a possible implementation form of the method according to anypreceding implementation of the second aspect or the second aspect assuch, wherein the sub-partitions are rectangular transform blocksub-partitions.

In a possible implementation form of the method according to anypreceding implementation of the second aspect or the second aspect assuch, wherein the current coding block is coded using an Intrasub-partition, ISP, tool.

According to a third aspect of the present disclosure, it is provided adevice for use in an image encoder and/or an image decoder, fordeblocking sub-partitions boundary within a coding block, wherein thecurrent coding block is coded in intra prediction mode and the currentcoding block is partitioned into sub-partitions comprising a firstsub-partition and a second sub-partition which is adjacent to the firstsub-partition, wherein the second sub-partition is intra predicted basedon the first sub-partition;

wherein the device comprises a de-blocking filter configured to:

determine a first maximum filter length to be 1 for the firstsub-partition and/or a second maximum filter length to be 1 for thesecond sub-partition when a width of the first sub-partition is 4samples or a width of the second sub-partition is 4 samples, or when aheight of the first sub-partition is 4 samples or a height of the secondsub-partition is 4 samples;

modify a value of up to one sample of the first sub-partition, whereinthe up to one sample is obtained from a row or column of the firstsub-partition that is perpendicular to and adjacent to thesub-partitions boundary between the first sub-partition and the secondsub-partition; and/or

modify a value of up to one sample of the second sub-partition, whereinthe up to one sample is obtained from a row or column of the secondsub-partition that is perpendicular to and adjacent to thesub-partitions boundary between the first sub-partition and the secondsub-partition.

According to a fourth aspect of the present disclosure, it is provided adevice for use in an image encoder and/or an image decoder, fordeblocking block edges between image blocks, wherein the block edgescomprises an edge between a current sub-partition of a current codingblock and a neighboring block of the current coding block, wherein thecurrent coding block is coded in intra prediction mode and the currentcoding block is partitioned into sub-partitions;

wherein the device comprises a de-blocking filter configured to:

determine a third maximum filter length to be 1 for the currentsub-partition and/or a fourth maximum filter length to be 1 for theneighboring block when a width of the current sub-partition is 4 samplesor a height of the current sub-partition is 4 samples;

modify a value of up to one sample of the current sub-partition, whereinthe up to one sample is obtained from a row or column of the currentsub-partition that is perpendicular to and adjacent to the edge betweenthe current sub-partition and the neighboring block; and/or

modify a value of up to one sample of the neighboring block, wherein theup to one sample is obtained from a row or column of the neighboringblock that is perpendicular to and adjacent to the edge between thecurrent sub-partition and the neighboring block.

The method according to the first aspect of the invention can beperformed by the apparatus according to the third aspect of theinvention. Further features and implementation forms of the apparatusaccording to the third aspect of the invention correspond to thefeatures and implementation forms of the method according to the firstaspect of the invention.

The method according to the second aspect of the invention can beperformed by the apparatus according to the fourth aspect of theinvention. Further features and implementation forms of the apparatusaccording to the fourth aspect of the invention correspond to thefeatures and implementation forms of the method according to the secondaspect of the invention.

According to a fifth aspect the invention relates to an apparatus fordecoding a video stream includes a processor and a memory. The memory isstoring instructions that cause the processor to perform the methodaccording to the first or second aspect.

According to a sixth aspect the invention relates to an apparatus forencoding a video stream includes a processor and a memory. The memory isstoring instructions that cause the processor to perform the methodaccording to the first or second aspect.

According to a seventh aspect, a computer-readable storage medium havingstored thereon instructions that when executed cause one or moreprocessors configured to code video data is proposed. The instructionscause the one or more processors to perform a method according to thefirst or second aspect or any possible embodiment of the first or secondaspect.

According to an eighth aspect, the invention relates to a computerprogram comprising program code for performing the method according tothe first or second aspect or any possible embodiment of the first orsecond aspect when executed on a computer.

According to a ninth aspect, the invention relates to an encoder or adecoder comprising processing circuitry for carrying out the methodaccording to the first or second aspect or any possible embodiment ofthe first or second aspect.

According to a tenth aspect of the invention, a video encoding apparatusis provided. The video encoding apparatus for encoding a picture of avideo stream, wherein the video encoding apparatus comprises:

a reconstruction unit configured to reconstruct the picture, wherein thereconstruction of the picture comprises generating a reconstructed blockof a current coding block which belongs to the picture, wherein thecurrent coding block is coded in intra prediction mode and the currentcoding block is partitioned into sub-partitions comprising a firstsub-partition and a second sub-partition, wherein the secondsub-partition is intra predicted based on the first sub-partition; anda filtering unit configured to process the reconstructed picture into afiltered reconstructed picture, wherein the filtering unit is configuredto filter up to one sample in a current sub-partition of reconstructedsub-partitions of the reconstructed block when a height of the currentsub-partition or another sub-partition that is adjacent to the currentsub-partition is 4 samples or when a width of the current sub-partitionor another sub-partition that is adjacent to the current sub-partitionis 4 samples, wherein the up to one sample is positioned in a row orcolumn of the current sub-partition perpendicular to a boundary betweenthe current sub-partition and said another sub-partition that ispositioned adjacent to the current sub-partition and the one sample isadjacent to the boundary, or wherein the filtering unit is configured tofilter a boundary between a current sub-partition of the reconstructedblock and a neighboring block which is adjacent to the currentsub-partition, based on a respective maximum filter length for thecurrent sub-partition and a respective maximum filter length for theneighboring block, and the respective maximum filter lengths are both 1when a height of the current sub-partition is 4 samples or when a widthof the current sub-partition is 4 samples.

This allows for efficiently improving the quality of reconstructedpictures in the framework of ISP.

In a possible implementation form of the up to one sample, which isobtained from the column of the first or second sub-partition that isperpendicular to and adjacent to the boundary between the first andsecond sub-partitions, is modified when a height of the first or secondsub-partition is 4 samples if an intra sub-partitions split type ofpartitioning the current coding block into sub-partitions is horizontal.It can be understood that, “the up to one sample is modified” may referto at most one sample is allowed to be modified. That is, depending onthe particular filtering decision phase, in some cases no sample may bemodified, or in other cases only one sample may be modified in eachcolumn perpendicular to and adjacent to the sub-partitions boundary.

In a possible implementation form the up to one sample, which isobtained from the row of the first or second sub-partition that isperpendicular to and adjacent to the boundary between the first andsecond sub-partitions, is modified when a width of the first or secondsub-partition is 4 samples if an intra sub-partitions split type ofpartitioning the current coding block into sub-partitions is vertical.It can be understood that, “the up to one sample is modified” may referto at most one sample is allowed to be modified. That is, depending onthe particular filtering decision phase, in some cases no sample may bemodified, or in other cases only one sample may be modified in each rowperpendicular to and adjacent to the sub-partitions boundary.

In a possible implementation form, if the intra sub-partitions splittype of partitioning the current coding block into sub-partitions ishorizontal, the sub-partitions boundary between the first and secondsub-partitions is a horizontal sub-partitions boundary; Alternatively,if the intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is vertical, the sub-partitionsboundary between the first and second sub-partitions is a verticalsub-partitions boundary.

In a possible implementation form, if the intra sub-partitions splittype of partitioning the current coding block into sub-partitions isvertical, the first sub-partition may be left to the secondsub-partition and the second sub-partition may be intra predicted basedon a reconstructed value of the first sub-partition;

if the intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is horizontal, the first sub-partitionmay be top of the second sub-partition and the second sub-partition maybe intra predicted based on a reconstructed value of the firstsub-partition.

It can be understood that, the second sub-partition is intra predictedbased on the reconstructed version (i.e. reconstructed values) of thefirst sub-partition. The reconstructed first sub-partition represents areference for intra prediction of the second sub-partition. It is notedthat after a current picture to which the current coding block belongsare reconstructed, the reconstructed picture is input to the filteringprocess. During the reconstruction of the current picture, the currentcoding block which is applied by the ISP coding tool is intra predictedto obtain the predictive block (e.g. predicted values) of the currentcoding block, in particular, the sub-partitions inside the current intracoding block are intra predicted one by one.

In a possible implementation form, the number of sub-partitions is 2 or4.

In a possible implementation form

if a width of the current coding block is equal to 4 and a height of thecoding block is equal to 8 and/or if the width of the current codingblock is equal to 8 and the height of the current coding block is equalto 4, the number of sub-partitions is 2,

otherwise, the number of sub-partitions is 4.

In a possible implementation form, the up to one sample in the first orsecond sub-partition is modified even if the sub-partitions boundarybetween the first and second sub-partitions is not overlapped with ann×n sample grid, wherein n is an integer.

It is allowed to de-blocking the target boundaries, which is not alignedwith an n×n grid, but is caused by ISP and is an internal boundarybetween sub-partitions of a coding block.

In a possible implementation form, the up to one sample in the first orsecond sub-partition is modified only if the sub-partitions boundarybetween the first and second sub-partitions overlaps with an n×n samplegrid, wherein n is an integer, for example, n=4 or n=8. Thereby, thecomputational load may be even further reduced.

Moreover, the filtering of up to one sample in the sub-partitions may beperformed only when the heights of all of the sub-partitions are 4samples or when the widths of all of the sub-partitions are 4 samples.Thereby, the computational load of the overall coding process may befurther reduced.

In general, the sub-partitions may be rectangular transform blocksub-partitions.

In a possible implementation form, the samples of the sub-partitions areluma samples, or the samples of the sub-partitions are chroma samples.

In a possible implementation form, the order of intra predicting thesub-partitions is from left to right if the intra sub-partitions splittype of partitioning the current coding block into sub-partitions isvertical or wherein the order of intra predicting the sub-partitions isfrom top to down if the intra sub-partitions split type of partitioningthe current coding block into sub-partitions is horizontal. That is, thepartitioning of the prediction block into the sub-partitions may beperformed in a vertical direction. In this case, the order of intrapredicting the sub-partitions is one by one from left to right.Alternatively, the partitioning of the prediction block into thesub-partitions may be performed in a horizontal direction. In this case,the order of intra predicting the two sub-partitions is one by one fromtop to down.

In the present disclosure, the current coding block is coded using anIntra sub-partition, ISP, tool or the sub-partitions boundary is causedby an Intra sub-partition, ISP, tool.

In general, boundary strengths of all boundaries between thesub-partitions of the coding block may be set to a constant valueindicating the strength of the filtering process (for example, 2) inorder to simplify the overall processing.

Moreover, coded block flag, CBF, values may be obtained corresponding totwo adjacent sub-partitions, determining a boundary strength of aboundary between two adjacent sub-partitions of the current block,according to the CBF values corresponding to the two adjacentsub-partitions and

the filtering decision whether filtering is performed or not may beperformed according to the determined boundary strength. At least one ofthe CBF values corresponding to two adjacent sub-partitions may be notequal to 0, where 0 implies that there is no residual data afterquantization of that sub-partition.

According to an eleventh aspect of the invention, a video decodingapparatus is provided. The video decoding apparatus for decoding apicture of an encoded video stream, wherein the video decoding apparatuscomprises:

a reconstruction unit configured to reconstruct the picture, wherein thereconstruction of the picture comprises generating a reconstructed blockof a current coding block which belongs to a current picture, whereinthe current coding block is coded in intra prediction mode and thecurrent coding block is partitioned into sub-partitions comprising afirst sub-partition and a second sub-partition, wherein the secondsub-partition is intra predicted based on the first sub-partition; anda filtering unit configured to process the reconstructed picture into afiltered reconstructed picture, wherein the filtering unit is configuredto filter up to one sample in a current sub-partition of reconstructedsub-partitions of the reconstructed block when a height of the currentsub-partition or another sub-partition that is adjacent to the currentsub-partition is 4 samples or when a width of the current sub-partitionor another sub-partition that is adjacent to the current sub-partitionis 4 samples, wherein the up to one sample is positioned in a row orcolumn of the current sub-partition perpendicular to a boundary betweenthe current sub-partition and said another sub-partition that ispositioned adjacent to the current sub-partition and the one sample isadjacent to the boundary, or wherein the filtering unit is configured tofilter a boundary between a current sub-partition of the reconstructedblock and a neighboring block which is adjacent to the currentsub-partition, based on a respective maximum filter length for thecurrent sub-partition and a respective maximum filter length for theneighboring block, and the respective maximum filter lengths are both 1when a height of the current sub-partition is 4 samples or when a widthof the current sub-partition is 4 samples.

This allows efficiently improving the quality of reconstructed picturesin the framework of ISP.

Further, it is provided an encoder, comprising means for encoding acurrent coding block of a current picture, wherein the means comprisesmeans for generating a reconstructed block of the current coding blockand means for filtering a reconstructed picture of the current pictureaccording to any one of the above-described embodiments of the inventivemethods.

Further, it is provided a decoder, comprising means for decoding acurrent coding block of a current picture, wherein the means comprisesmeans for generating a reconstructed block of the current coding blockand means for filtering a reconstructed picture of the current pictureaccording to any one of the above-described embodiments of the inventivemethods.

Details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments of the invention are described in moredetail with reference to the attached figures and drawings, in which:

FIG. 1A is a block diagram showing an example of a video coding systemconfigured to implement embodiments of the invention;

FIG. 1B is a block diagram showing another example of a video codingsystem configured to implement embodiments of the invention;

FIG. 2 is a block diagram showing an example of a video encoderconfigured to implement embodiments of the invention;

FIG. 3 is a block diagram showing an example structure of a videodecoder configured to implement embodiments of the invention;

FIG. 4 is a block diagram illustrating an example of an encodingapparatus or a decoding apparatus;

FIG. 5 is a block diagram illustrating another example of an encodingapparatus or a decoding apparatus;

FIG. 6 is a block diagram illustrating an example of deblockingsub-partition edges within a coding unit (CU) which uses an Intrasub-partition (ISP) tool;

FIG. 7 is a block diagram illustrating another example of deblockingsub-partition edges within a CU which uses an Intra sub-partition (ISP)tool;

FIG. 8 is a block diagram illustrating an example of deblockingsub-partition edges within a CU which overlap with an 8×8 sample grid;

FIG. 9 is a block diagram illustrating an example of deblocking allsub-partition edges within a CU which overlap with a 4×4 sample grid;

FIG. 10 is a block diagram illustrating an example according to whichwhen sub-partitions size is <8 samples orthogonally in the direction ofdeblocking, then a weak filter which only uses 3 samples in deblockingdecision and which modifies only one sample is used;

FIG. 11 shows a flow diagram depicting an exemplary process fordeblocking filtering;

FIG. 12 shows a flow diagram depicting another exemplary process fordeblocking filtering;

FIG. 13 shows a schematic diagram of a device for de-blockingsub-partitions boundary within a coding block.

FIG. 14 shows a schematic diagram of a device for de-blocking blockedges.

FIG. 15 shows a flow diagram depicting an exemplary process of codingimplemented in a decoding device or an encoding device;

FIG. 16 shows a flow diagram depicting another exemplary process ofcoding implemented in a decoding device or an encoding device;

FIG. 17 shows a schematic diagram of a device for video coding;

FIG. 18 shows a schematic diagram of a device for video coding;

FIG. 19 is a block diagram showing an example structure of a contentsupply system which realizes a content delivery service; and

FIG. 20 is a block diagram showing a structure of an example of aterminal device.

In the following identical reference signs refer to identical or atleast functionally equivalent features if not explicitly specifiedotherwise.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanyingfigures, which form part of the disclosure, and which show, by way ofillustration, specific aspects of embodiments of the invention orspecific aspects in which embodiments of the present invention may beused. It is understood that embodiments of the invention may be used inother aspects and comprise structural or logical changes not depicted inthe figures. The following detailed description, therefore, is not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims.

For instance, it is understood that disclosure in connection with adescribed method may also hold true for a corresponding device or systemconfigured to perform the method and vice versa. For example, if one ora plurality of specific method steps are described, a correspondingdevice may include one or a plurality of units, e.g. functional units,to perform the described one or plurality of method steps (e.g. one unitperforming the one or plurality of steps, or a plurality of units eachperforming one or more of the plurality of steps), even if such one ormore units are not explicitly described or illustrated in the figures.On the other hand, for example, if a specific apparatus is describedbased on one or a plurality of units, e.g. functional units, acorresponding method may include one step to perform the functionalityof the one or plurality of units (e.g. one step performing thefunctionality of the one or plurality of units, or a plurality of stepseach performing the functionality of one or more of the plurality ofunits), even if such one or plurality of steps are not explicitlydescribed or illustrated in the figures. Further, it is understood thatthe features of the various exemplary embodiments and/or aspectsdescribed herein may be combined with each other, unless specificallynoted otherwise.

Video coding typically refers to the processing of a sequence ofpictures, which form the video or video sequence. Instead of the term“picture” the term “frame” or “image” may be used as synonyms in thefield of video coding. Video coding (or coding in general) comprises twoparts video encoding and video decoding. Video encoding is performed atthe source side, typically comprising processing (e.g. by compression)the original video pictures to reduce the amount of data required forrepresenting the video pictures (for more efficient storage and/ortransmission). Video decoding is performed at the destination side andtypically comprises the inverse processing compared to the encoder toreconstruct the video pictures. Embodiments referring to “coding” ofvideo pictures (or pictures in general) shall be understood to relate to“encoding” or “decoding” of video pictures or respective videosequences. The combination of the encoding part and the decoding part isalso referred to as CODEC (Coding and Decoding).

In case of lossless video coding, the original video pictures can bereconstructed, i.e. the reconstructed video pictures have the samequality as the original video pictures (assuming no transmission loss orother data loss during storage or transmission). In case of lossy videocoding, further compression, e.g. by quantization, is performed, toreduce the amount of data representing the video pictures, which cannotbe completely reconstructed at the decoder, i.e. the quality of thereconstructed video pictures is lower or worse compared to the qualityof the original video pictures.

Several video coding standards belong to the group of “lossy hybridvideo codecs” (i.e. combine spatial and temporal prediction in thesample domain and 2D transform coding for applying quantization in thetransform domain). Each picture of a video sequence is typicallypartitioned into a set of non-overlapping blocks and the coding istypically performed on a block level. In other words, at the encoder thevideo is typically processed, i.e. encoded, on a block (video block)level, e.g. by using spatial (intra picture) prediction and/or temporal(inter picture) prediction to generate a prediction block, subtractingthe prediction block from the current block (block currentlyprocessed/to be processed) to obtain a residual block, transforming theresidual block and quantizing the residual block in the transform domainto reduce the amount of data to be transmitted (compression), whereas atthe decoder the inverse processing compared to the encoder is applied tothe encoded or compressed block to reconstruct the current block forrepresentation. Furthermore, the encoder duplicates the decoderprocessing loop such that both will generate identical predictions (e.g.intra- and inter predictions) and/or re-constructions for processing,i.e. coding, the subsequent blocks.

In the following embodiments of a video coding system 10, a videoencoder 20 and a video decoder 30 are described based on FIGS. 1 to 3.

FIG. 1A is a schematic block diagram illustrating an example codingsystem 10, e.g. a video coding system 10 (or short coding system 10)that may utilize techniques of this present application. Video encoder20 (or short encoder 20) and video decoder 30 (or short decoder 30) ofvideo coding system 10 represent examples of devices that may beconfigured to perform techniques in accordance with various examplesdescribed in the present application.

As shown in FIG. 1A, the coding system 10 comprises a source device 12configured to provide encoded picture data 21 e.g. to a destinationdevice 14 for decoding the encoded picture data 13.

The source device 12 comprises an encoder 20, and may additionally, i.e.optionally, comprise a picture source 16, a pre-processor (orpre-processing unit) 18, e.g. a picture pre-processor 18, and acommunication interface or communication unit 22.

The picture source 16 may comprise or be any kind of picture capturingdevice, for example a camera for capturing a real-world picture, and/orany kind of a picture generating device, for example a computer-graphicsprocessor for generating a computer animated picture, or any kind ofother device for obtaining and/or providing a real-world picture, acomputer generated picture (e.g. a screen content, a virtual reality(VR) picture) and/or any combination thereof (e.g. an augmented reality(AR) picture). The picture source may be any kind of memory or storagestoring any of the aforementioned pictures.

In distinction to the pre-processor 18 and the processing performed bythe pre-processing unit 18, the picture or picture data 17 may also bereferred to as raw picture or raw picture data 17.

Pre-processor 18 is configured to receive the (raw) picture data 17 andto perform pre-processing on the picture data 17 to obtain apre-processed picture 19 or pre-processed picture data 19.Pre-processing performed by the pre-processor 18 may, e.g., comprisetrimming, color format conversion (e.g. from RGB to YCbCr), colorcorrection, or de-noising. It can be understood that the pre-processingunit 18 may be optional component.

The video encoder 20 is configured to receive the pre-processed picturedata 19 and provide encoded picture data 21 (further details will bedescribed below, e.g., based on FIG. 2).

Communication interface 22 of the source device 12 may be configured toreceive the encoded picture data 21 and to transmit the encoded picturedata 21 (or any further processed version thereof) over communicationchannel 13 to another device, e.g. the destination device 14 or anyother device, for storage or direct reconstruction.

The destination device 14 comprises a decoder 30 (e.g. a video decoder30), and may additionally, i.e. optionally, comprise a communicationinterface or communication unit 28, a post-processor 32 (orpost-processing unit 32) and a display device 34.

The communication interface 28 of the destination device 14 isconfigured receive the encoded picture data 21 (or any further processedversion thereof), e.g. directly from the source device 12 or from anyother source, e.g. a storage device, e.g. an encoded picture datastorage device, and provide the encoded picture data 21 to the decoder30.

The communication interface 22 and the communication interface 28 may beconfigured to transmit or receive the encoded picture data 21 or encodeddata 13 via a direct communication link between the source device 12 andthe destination device 14, e.g. a direct wired or wireless connection,or via any kind of network, e.g. a wired or wireless network or anycombination thereof, or any kind of private and public network, or anykind of combination thereof.

The communication interface 22 may be, e.g., configured to package theencoded picture data 21 into an appropriate format, e.g. packets, and/orprocess the encoded picture data using any kind of transmission encodingor processing for transmission over a communication link orcommunication network.

The communication interface 28, forming the counterpart of thecommunication interface 22, may be, e.g., configured to receive thetransmitted data and process the transmission data using any kind ofcorresponding transmission decoding or processing and/or de-packaging toobtain the encoded picture data 21.

Both, communication interface 22 and communication interface 28 may beconfigured as unidirectional communication interfaces as indicated bythe arrow for the communication channel 13 in FIG. 1A pointing from thesource device 12 to the destination device 14, or bi-directionalcommunication interfaces, and may be configured, e.g. to send andreceive messages, e.g. to set up a connection, to acknowledge andexchange any other information related to the communication link and/ordata transmission, e.g. encoded picture data transmission.

The decoder 30 is configured to receive the encoded picture data 21 andprovide decoded picture data 31 or a decoded picture 31 (further detailswill be described below, e.g., based on FIG. 3 or FIG. 5).

The post-processor 32 of destination device 14 is configured topost-process the decoded picture data 31 (also called reconstructedpicture data), e.g. the decoded picture 31, to obtain post-processedpicture data 33, e.g. a post-processed picture 33. The post-processingperformed by the post-processing unit 32 may comprise, e.g. color formatconversion (e.g. from YCbCr to RGB), color correction, trimming, orre-sampling, or any other processing, e.g. for preparing the decodedpicture data 31 for display, e.g. by display device 34.

The display device 34 of the destination device 14 is configured toreceive the post-processed picture data 33 for displaying the picture,e.g. to a user or viewer. The display device 34 may be or comprise anykind of display for representing the reconstructed picture, e.g. anintegrated or external display or monitor. The displays may, e.g.comprise liquid crystal displays (LCD), organic light emitting diodes(OLED) displays, plasma displays, projectors, micro LED displays, liquidcrystal on silicon (LCoS), digital light processor (DLP) or any kind ofother display.

Although FIG. 1A depicts the source device 12 and the destination device14 as separate devices, embodiments of devices may also comprise both orboth functionalities, the source device 12 or correspondingfunctionality and the destination device 14 or correspondingfunctionality. In such embodiments the source device 12 or correspondingfunctionality and the destination device 14 or correspondingfunctionality may be implemented using the same hardware and/or softwareor by separate hardware and/or software or any combination thereof.

As will be apparent for the skilled person based on the description, theexistence and (exact) split of functionalities of the different units orfunctionalities within the source device 12 and/or destination device 14as shown in FIG. 1A may vary depending on the actual device andapplication.

The encoder 20 (e.g. a video encoder 20) or the decoder 30 (e.g. a videodecoder 30) or both encoder 20 and decoder 30 may be implemented viaprocessing circuitry as shown in FIG. 1B, such as one or moremicroprocessors, digital signal processors (DSPs), application-specificintegrated circuits (ASICs), field-programmable gate arrays (FPGAs),discrete logic, hardware, video coding dedicated or any combinationsthereof. The encoder 20 may be implemented via processing circuitry 46to embody the various modules as discussed with respect to encoder 20 ofFIG. 2 and/or any other encoder system or subsystem described herein.The decoder 30 may be implemented via processing circuitry 46 to embodythe various modules as discussed with respect to decoder 30 of FIG. 3and/or any other decoder system or subsystem described herein. Theprocessing circuitry may be configured to perform the various operationsas discussed later. As shown in FIG. 5, if the techniques areimplemented partially in software, a device may store instructions forthe software in a suitable, non-transitory computer-readable storagemedium and may execute the instructions in hardware using one or moreprocessors to perform the techniques of this disclosure. Either of videoencoder 20 and video decoder 30 may be integrated as part of a combinedencoder/decoder (CODEC) in a single device, for example, as shown inFIG. 1B.

Source device 12 and destination device 14 may comprise any of a widerange of devices, including any kind of handheld or stationary devices,e.g. notebook or laptop computers, mobile phones, smart phones, tabletsor tablet computers, cameras, desktop computers, set-top boxes,televisions, display devices, digital media players, video gamingconsoles, video streaming devices (such as content services servers orcontent delivery servers), broadcast receiver device, broadcasttransmitter device, or the like and may use no or any kind of operatingsystem. In some cases, the source device 12 and the destination device14 may be equipped for wireless communication. Thus, the source device12 and the destination device 14 may be wireless communication devices.

In some cases, video coding system 10 illustrated in FIG. 1A is merelyan example and the techniques of the present application may apply tovideo coding settings (e.g., video encoding or video decoding) that donot necessarily include any data communication between the encoding anddecoding devices. In other examples, data is retrieved from a localmemory, streamed over a network, or the like. A video encoding devicemay encode and store data to memory, and/or a video decoding device mayretrieve and decode data from memory. In some examples, the encoding anddecoding is performed by devices that do not communicate with oneanother, but simply encode data to memory and/or retrieve and decodedata from memory.

For convenience of description, embodiments of the invention aredescribed herein, for example, by reference to High-Efficiency VideoCoding (HEVC) or to the reference software of Versatile Video coding(VVC), the next generation video coding standard developed by the JointCollaboration Team on Video Coding (JCT-VC) of ITU-T Video CodingExperts Group (VCEG) and ISO/IEC Motion Picture Experts Group (MPEG).One of ordinary skill in the art will understand that embodiments of theinvention are not limited to HEVC or VVC.

Encoder and Encoding Method

FIG. 2 shows a schematic block diagram of an example video encoder 20that is configured to implement the techniques of the presentapplication. In the example of FIG. 2, the video encoder 20 comprises aninput 201 (or input interface 201), a residual calculation unit 204, atransform processing unit 206, a quantization unit 208, an inversequantization unit 210, and inverse transform processing unit 212, areconstruction unit 214, a loop filter unit 220, a decoded picturebuffer (DPB) 230, a mode selection unit 260, an entropy encoding unit270 and an output 272 (or output interface 272). The mode selection unit260 may include an inter prediction unit 244, an intra prediction unit254 and a partitioning unit 262. Inter prediction unit 244 may include amotion estimation unit and a motion compensation unit (not shown). Avideo encoder 20 as shown in FIG. 2 may also be referred to as hybridvideo encoder or a video encoder according to a hybrid video codec.

The residual calculation unit 204, the transform processing unit 206,the quantization unit 208, the mode selection unit 260 may be referredto as forming a forward signal path of the encoder 20, whereas theinverse quantization unit 210, the inverse transform processing unit212, the reconstruction unit 214, the buffer 216, the loop filter 220,the decoded picture buffer (DPB) 230, the inter prediction unit 244 andthe intra-prediction unit 254 may be referred to as forming a backwardsignal path of the video encoder 20, wherein the backward signal path ofthe video encoder 20 corresponds to the signal path of the decoder (seevideo decoder 30 in FIG. 3). The inverse quantization unit 210, theinverse transform processing unit 212, the reconstruction unit 214, theloop filter 220, the decoded picture buffer (DPB) 230, the interprediction unit 244 and the intra-prediction unit 254 are also referredto forming the “built-in decoder” of video encoder 20.

Pictures & Picture Partitioning (Pictures & Blocks)

The encoder 20 may be configured to receive, e.g. via input 201, apicture 17 (or picture data 17), e.g. picture of a sequence of picturesforming a video or video sequence. The received picture or picture datamay also be a pre-processed picture 19 (or pre-processed picture data19). For sake of simplicity the following description refers to thepicture 17. The picture 17 may also be referred to as current picture orpicture to be coded (in particular in video coding to distinguish thecurrent picture from other pictures, e.g. previously encoded and/ordecoded pictures of the same video sequence, i.e. the video sequencewhich also comprises the current picture).

A (digital) picture is or can be regarded as a two-dimensional array ormatrix of samples with intensity values. A sample in the array may alsobe referred to as pixel (short form of picture element) or a pel. Thenumber of samples in horizontal and vertical direction (or axis) of thearray or picture define the size and/or resolution of the picture. Forrepresentation of color, typically three color components are employed,i.e. the picture may be represented or include three sample arrays. InRBG format or color space a picture comprises a corresponding red, greenand blue sample array. However, in video coding each pixel is typicallyrepresented in a luminance and chrominance format or color space, e.g.YCbCr, which comprises a luminance component indicated by Y (sometimesalso L is used instead) and two chrominance components indicated by Cband Cr. The luminance (or short luma) component Y represents thebrightness or grey level intensity (e.g. like in a grey-scale picture),while the two chrominance (or short chroma) components Cb and Crrepresent the chromaticity or color information components. Accordingly,a picture in YCbCr format comprises a luminance sample array ofluminance sample values (Y), and two chrominance sample arrays ofchrominance values (Cb and Cr). Pictures in RGB format may be convertedor transformed into YCbCr format and vice versa, the process is alsoknown as color transformation or conversion. If a picture is monochrome,the picture may comprise only a luminance sample array. Accordingly, apicture may be, for example, an array of luma samples in monochromeformat or an array of luma samples and two corresponding arrays ofchroma samples in 4:2:0, 4:2:2, and 4:4:4 colour format.

Embodiments of the video encoder 20 may comprise a picture partitioningunit (not depicted in FIG. 2) configured to partition the picture 17into a plurality of (typically non-overlapping) picture blocks 203.These blocks may also be referred to as root blocks, macro blocks(H.264/AVC) or coding tree blocks (CTB) or coding tree units (CTU)(H.265/HEVC and VVC). The picture partitioning unit may be configured touse the same block size for all pictures of a video sequence and thecorresponding grid defining the block size, or to change the block sizebetween pictures or subsets or groups of pictures, and partition eachpicture into the corresponding blocks.

In further embodiments, the video encoder may be configured to receivedirectly a block 203 of the picture 17, e.g. one, several or all blocksforming the picture 17. The picture block 203 may also be referred to ascurrent picture block or picture block to be coded.

Like the picture 17, the picture block 203 again is or can be regardedas a two-dimensional array or matrix of samples with intensity values(sample values), although of smaller dimension than the picture 17. Inother words, the block 203 may comprise, e.g., one sample array (e.g. aluma array in case of a monochrome picture 17, or a luma or chroma arrayin case of a color picture) or three sample arrays (e.g. a luma and twochroma arrays in case of a color picture 17) or any other number and/orkind of arrays depending on the color format applied. The number ofsamples in horizontal and vertical direction (or axis) of the block 203define the size of block 203. Accordingly, a block may, for example, anM×N (M-column by N-row) array of samples, or an M×N array of transformcoefficients.

Embodiments of the video encoder 20 as shown in FIG. 2 may be configuredto encode the picture 17 block by block, e.g. the encoding andprediction is performed per block 203.

Embodiments of the video encoder 20 as shown in FIG. 2 may be furtherconfigured to partition and/or encode the picture by using slices (alsoreferred to as video slices), wherein a picture may be partitioned intoor encoded using one or more slices (typically non-overlapping), andeach slice may comprise one or more blocks (e.g. CTUs).

Embodiments of the video encoder 20 as shown in FIG. 2 may be furtherconfigured to partition and/or encode the picture by using tile groups(also referred to as video tile groups) and/or tiles (also referred toas video tiles), wherein a picture may be partitioned into or encodedusing one or more tile groups (typically non-overlapping), and each tilegroup may comprise, e.g. one or more blocks (e.g. CTUs) or one or moretiles, wherein each tile, e.g. may be of rectangular shape and maycomprise one or more blocks (e.g. CTUs), e.g. complete or fractionalblocks.

Residual Calculation

The residual calculation unit 204 may be configured to calculate aresidual block 205 (also referred to as residual 205) based on thepicture block 203 and a prediction block 265 (further details about theprediction block 265 are provided later), e.g. by subtracting samplevalues of the prediction block 265 from sample values of the pictureblock 203, sample by sample (pixel by pixel) to obtain the residualblock 205 in the sample domain.

Transform

The transform processing unit 206 may be configured to apply atransform, e.g. a discrete cosine transform (DCT) or discrete sinetransform (DST), on the sample values of the residual block 205 toobtain transform coefficients 207 in a transform domain. The transformcoefficients 207 may also be referred to as transform residualcoefficients and represent the residual block 205 in the transformdomain.

The transform processing unit 206 may be configured to apply integerapproximations of DCT/DST, such as the transforms specified forH.265/HEVC. Compared to an orthogonal DCT transform, such integerapproximations are typically scaled by a certain factor. In order topreserve the norm of the residual block which is processed by forwardand inverse transforms, additional scaling factors are applied as partof the transform process. The scaling factors are typically chosen basedon certain constraints like scaling factors being a power of two forshift operations, bit depth of the transform coefficients, tradeoffbetween accuracy and implementation costs, etc. Specific scaling factorsare, for example, specified for the inverse transform, e.g. by inversetransform processing unit 212 (and the corresponding inverse transform,e.g. by inverse transform processing unit 312 at video decoder 30) andcorresponding scaling factors for the forward transform, e.g. bytransform processing unit 206, at an encoder 20 may be specifiedaccordingly.

Embodiments of the video encoder 20 (respectively transform processingunit 206) may be configured to output transform parameters, e.g. a typeof transform or transforms, e.g. directly or encoded or compressed viathe entropy encoding unit 270, so that, e.g., the video decoder 30 mayreceive and use the transform parameters for decoding.

Quantization

The quantization unit 208 may be configured to quantize the transformcoefficients 207 to obtain quantized coefficients 209, e.g. by applyingscalar quantization or vector quantization. The quantized coefficients209 may also be referred to as quantized transform coefficients 209 orquantized residual coefficients 209.

The quantization process may reduce the bit depth associated with someor all of the transform coefficients 207. For example, an n-bittransform coefficient may be rounded down to an m-bit Transformcoefficient during quantization, where n is greater than m. The degreeof quantization may be modified by adjusting a quantization parameter(QP). For example for scalar quantization, different scaling may beapplied to achieve finer or coarser quantization. Smaller quantizationstep sizes correspond to finer quantization, whereas larger quantizationstep sizes correspond to coarser quantization. The applicablequantization step size may be indicated by a quantization parameter(QP). The quantization parameter may for example be an index to apredefined set of applicable quantization step sizes. For example, smallquantization parameters may correspond to fine quantization (smallquantization step sizes) and large quantization parameters maycorrespond to coarse quantization (large quantization step sizes) orvice versa. The quantization may include division by a quantization stepsize and a corresponding and/or the inverse dequantization, e.g. byinverse quantization unit 210, may include multiplication by thequantization step size. Embodiments according to some standards, e.g.HEVC, may be configured to use a quantization parameter to determine thequantization step size. Generally, the quantization step size may becalculated based on a quantization parameter using a fixed pointapproximation of an equation including division. Additional scalingfactors may be introduced for quantization and dequantization to restorethe norm of the residual block, which might get modified because of thescaling used in the fixed point approximation of the equation forquantization step size and quantization parameter. In one exampleimplementation, the scaling of the inverse transform and dequantizationmight be combined. Alternatively, customized quantization tables may beused and signaled from an encoder to a decoder, e.g. in a bitstream. Thequantization is a lossy operation, wherein the loss increases withincreasing quantization step sizes.

Embodiments of the video encoder 20 (respectively quantization unit 208)may be configured to output quantization parameters (QP), e.g. directlyor encoded via the entropy encoding unit 270, so that, e.g., the videodecoder 30 may receive and apply the quantization parameters fordecoding.

Inverse Quantization

The inverse quantization unit 210 is configured to apply the inversequantization of the quantization unit 208 on the quantized coefficientsto obtain dequantized coefficients 211, e.g. by applying the inverse ofthe quantization scheme applied by the quantization unit 208 based on orusing the same quantization step size as the quantization unit 208. Thedequantized coefficients 211 may also be referred to as dequantizedresidual coefficients 211 and correspond

although typically not identical to the transform coefficients due tothe loss by quantization—to the transform coefficients 207.

Inverse Transform

The inverse transform processing unit 212 is configured to apply theinverse transform of the transform applied by the transform processingunit 206, e.g. an inverse discrete cosine transform (DCT) or inversediscrete sine transform (DST) or other inverse transforms, to obtain areconstructed residual block 213 (or corresponding dequantizedcoefficients 213) in the sample domain. The reconstructed residual block213 may also be referred to as (reconstructed) transform block 213.

Reconstruction

The reconstruction unit 214 (e.g. adder or summer 214) is configured toadd the (reconstructed) transform block 213 (i.e. reconstructed residualblock 213) to the prediction block 265 to obtain a reconstructed block215 in the sample domain, e.g. by adding—sample by sample—the samplevalues of the reconstructed residual block 213 and the sample values ofthe prediction block 265.

Filtering

The loop filter unit 220 (or short “loop filter” 220), is configured tofilter the reconstructed block 215 to obtain a filtered block 221, or ingeneral, to filter reconstructed samples to obtain filtered samples. Theloop filter unit is, e.g., configured to smooth pixel transitions, orotherwise improve the video quality. The loop filter unit 220 maycomprise one or more loop filters such as a de-blocking filter, asample-adaptive offset (SAO) filter or one or more other filters, e.g. abilateral filter, an adaptive loop filter (ALF), a sharpening, asmoothing filters or a collaborative filters, or any combinationthereof. Although the loop filter unit 220 is shown in FIG. 2 as beingan in loop filter, in other configurations, the loop filter unit 220 maybe implemented as a post loop filter. The filtered block 221 may also bereferred to as filtered reconstructed block 221.

Embodiments of the video encoder 20 (respectively loop filter unit 220)may be configured to output loop filter parameters (such as sampleadaptive offset information), e.g. directly or encoded via the entropyencoding unit 270, so that, e.g., a decoder 30 may receive and apply thesame loop filter parameters or respective loop filters for decoding.

Decoded Picture Buffer

The decoded picture buffer (DPB) 230 may be a memory that storesreference pictures, or in general reference picture data, for encodingvideo data by video encoder 20. The DPB 230 may be formed by any of avariety of memory devices, such as dynamic random access memory (DRAM),including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM),resistive RAM (RRAM), or other types of memory devices. The decodedpicture buffer (DPB) 230 may be configured to store one or more filteredblocks 221. The decoded picture buffer 230 may be further configured tostore other previously filtered blocks, e.g. previously reconstructedand filtered blocks 221, of the same current picture or of differentpictures, e.g. previously reconstructed pictures, and may providecomplete previously reconstructed, i.e. decoded, pictures (andcorresponding reference blocks and samples) and/or a partiallyreconstructed current picture (and corresponding reference blocks andsamples), for example for inter prediction. The decoded picture buffer(DPB) 230 may be also configured to store one or more unfilteredreconstructed blocks 215, or in general unfiltered reconstructedsamples, e.g. if the reconstructed block 215 is not filtered by loopfilter unit 220, or any other further processed version of thereconstructed blocks or samples.

Mode Selection (Partitioning & Prediction)

The mode selection unit 260 comprises partitioning unit 262,inter-prediction unit 244 and intra-prediction unit 254, and isconfigured to receive or obtain original picture data, e.g. an originalblock 203 (current block 203 of the current picture 17), andreconstructed picture data, e.g. filtered and/or unfilteredreconstructed samples or blocks of the same (current) picture and/orfrom one or a plurality of previously decoded pictures, e.g. fromdecoded picture buffer 230 or other buffers (e.g. line buffer, notshown). The reconstructed picture data is used as reference picture datafor prediction, e.g. inter-prediction or intra-prediction, to obtain aprediction block 265 or predictor 265.

Mode selection unit 260 may be configured to determine or select apartitioning for a current block prediction mode (including nopartitioning) and a prediction mode (e.g. an intra or inter predictionmode) and generate a corresponding prediction block 265, which is usedfor the calculation of the residual block 205 and for the reconstructionof the reconstructed block 215.

Embodiments of the mode selection unit 260 may be configured to selectthe partitioning and the prediction mode (e.g. from those supported byor available for mode selection unit 260), which provide the best matchor in other words the minimum residual (minimum residual means bettercompression for transmission or storage), or a minimum signalingoverhead (minimum signaling overhead means better compression fortransmission or storage), or which considers or balances both. The modeselection unit 260 may be configured to determine the partitioning andprediction mode based on rate distortion optimization (RDO), i.e. selectthe prediction mode which provides a minimum rate distortion. Terms like“best”, “minimum”, “optimum” etc. in this context do not necessarilyrefer to an overall “best”, “minimum”, “optimum”, etc. but may alsorefer to the fulfillment of a termination or selection criterion like avalue exceeding or falling below a threshold or other constraintsleading potentially to a “sub-optimum selection” but reducing complexityand processing time.

In other words, the partitioning unit 262 may be configured to partitionthe block 203 into smaller block partitions or sub-blocks (which formagain blocks), e.g. iteratively using quad-tree-partitioning (QT),binary partitioning (BT) or triple-tree-partitioning (TT) or anycombination thereof, and to perform, e.g., the prediction for each ofthe block partitions or sub-blocks, wherein the mode selection comprisesthe selection of the tree-structure of the partitioned block 203 and theprediction modes are applied to each of the block partitions orsub-blocks.

In the following the partitioning (e.g. by partitioning unit 260) andprediction processing (by inter-prediction unit 244 and intra-predictionunit 254) performed by an example video encoder 20 will be explained inmore detail.

Partitioning

The partitioning unit 262 may partition (or split) a current block 203into smaller partitions, e.g. smaller blocks of square or rectangularsize. These smaller blocks (which may also be referred to as sub-blocks)may be further partitioned into even smaller partitions. This is alsoreferred to tree-partitioning or hierarchical tree-partitioning, whereina root block, e.g. at root tree-level 0 (hierarchy-level 0, depth 0),may be recursively partitioned, e.g. partitioned into two or more blocksof a next lower tree-level, e.g. nodes at tree-level 1 (hierarchy-level1, depth 1), wherein these blocks may be again partitioned into two ormore blocks of a next lower level, e.g. tree-level 2 (hierarchy-level 2,depth 2), etc. until the partitioning is terminated, e.g. because atermination criterion is fulfilled, e.g. a maximum tree depth or minimumblock size is reached. Blocks which are not further partitioned are alsoreferred to as leaf-blocks or leaf nodes of the tree. A tree usingpartitioning into two partitions is referred to as binary-tree (BT), atree using partitioning into three partitions is referred to asternary-tree (TT), and a tree using partitioning into four partitions isreferred to as quad-tree (QT).

As mentioned before, the term “block” as used herein may be a portion,in particular, a square or rectangular portion, of a picture. Withreference, for example, to HEVC and VVC, the block may be or correspondto a coding tree unit (CTU), a coding unit (CU), prediction unit (PU),and transform unit (TU) and/or to the corresponding blocks, e.g. acoding tree block (CTB), a coding block (CB), a transform block (TB) orprediction block (PB).

For example, a coding tree unit (CTU) may be or comprise a CTB of lumasamples, two corresponding CTBs of chroma samples of a picture that hasthree sample arrays, or a CTB of samples of a monochrome picture or apicture that is coded using three separate colour planes and syntaxstructures used to code the samples. Correspondingly, a coding treeblock (CTB) may be an N×N block of samples for some value of N such thatthe division of a component into CTBs is a partitioning. A coding unit(CU) may be or comprise a coding block of luma samples, twocorresponding coding blocks of chroma samples of a picture that hasthree sample arrays, or a coding block of samples of a monochromepicture or a picture that is coded using three separate colour planesand syntax structures used to code the samples. Correspondingly a codingblock (CB) may be an M×N block of samples for some values of M and Nsuch that the division of a CTB into coding blocks is a partitioning.

In embodiments, e.g., according to HEVC, a coding tree unit (CTU) may besplit into CUs by using a quad-tree structure denoted as coding tree.The decision whether to code a picture area using inter-picture(temporal) or intra-picture (spatial) prediction is made at the CUlevel. Each CU can be further split into one, two or four PUs accordingto the PU splitting type. Inside one PU, the same prediction process isapplied and the relevant information is transmitted to the decoder on aPU basis. After obtaining the residual block by applying the predictionprocess based on the PU splitting type, a CU can be partitioned intotransform units (TUs) according to another quadtree structure similar tothe coding tree for the CU.

In embodiments, e.g., according to the latest video coding standardcurrently in development, which is referred to as Versatile Video Coding(VVC), a combined Quad-tree and binary tree (QTBT) partitioning is forexample used to partition a coding block. In the QTBT block structure, aCU can have either a square or rectangular shape. For example, a codingtree unit (CTU) is first partitioned by a quadtree structure. Thequadtree leaf nodes are further partitioned by a binary tree or ternary(or triple) tree structure. The partitioning tree leaf nodes are calledcoding units (CUs), and that segmentation is used for prediction andtransform processing without any further partitioning. This means thatthe CU, PU and TU have the same block size in the QTBT coding blockstructure. In parallel, multiple partition, for example, triple treepartition may be used together with the QTBT block structure.

In one example, the mode selection unit 260 of video encoder 20 may beconfigured to perform any combination of the partitioning techniquesdescribed herein.

As described above, the video encoder 20 is configured to determine orselect the best or an optimum prediction mode from a set of (e.g.pre-determined) prediction modes. The set of prediction modes maycomprise, e.g., intra-prediction modes and/or inter-prediction modes.

Intra-Prediction

The set of intra-prediction modes may comprise 35 differentintra-prediction modes, e.g. non-directional modes like DC (or mean)mode and planar mode, or directional modes, e.g. as defined in HEVC, ormay comprise 67 different intra-prediction modes, e.g. non-directionalmodes like DC (or mean) mode and planar mode, or directional modes, e.g.as defined for VVC.

The intra-prediction unit 254 is configured to use reconstructed samplesof neighboring blocks of the same current picture to generate anintra-prediction block 265 according to an intra-prediction mode of theset of intra-prediction modes.

The intra prediction unit 254 (or in general the mode selection unit260) is further configured to output intra-prediction parameters (or ingeneral information indicative of the selected intra prediction mode forthe block) to the entropy encoding unit 270 in form of syntax elements266 for inclusion into the encoded picture data 21, so that, e.g., thevideo decoder 30 may receive and use the prediction parameters fordecoding.

Inter-Prediction

The set of (or possible) inter-prediction modes depends on the availablereference pictures (i.e. previous at least partially decoded pictures,e.g. stored in DBP 230) and other inter-prediction parameters, e.g.whether the whole reference picture or only a part, e.g. a search windowarea around the area of the current block, of the reference picture isused for searching for a best matching reference block, and/or e.g.whether pixel interpolation is applied, e.g. half/semi-pel and/orquarter-pel interpolation, or not.

Additional to the above prediction modes, skip mode and/or direct modemay be applied.

The inter prediction unit 244 may include a motion estimation (ME) unitand a motion compensation (MC) unit (both not shown in FIG. 2). Themotion estimation unit may be configured to receive or obtain thepicture block 203 (current picture block 203 of the current picture 17)and a decoded picture 231, or at least one or a plurality of previouslyreconstructed blocks, e.g. reconstructed blocks of one or a plurality ofother/different previously decoded pictures 231, for motion estimation.E.g. a video sequence may comprise the current picture and thepreviously decoded pictures 231, or in other words, the current pictureand the previously decoded pictures 231 may be part of or form asequence of pictures forming a video sequence.

The encoder 20 may, e.g., be configured to select a reference block froma plurality of reference blocks of the same or different pictures of theplurality of other pictures and provide a reference picture (orreference picture index) and/or an offset (spatial offset) between theposition (x, y coordinates) of the reference block and the position ofthe current block as inter prediction parameters to the motionestimation unit. This offset is also called motion vector (MV).

The motion compensation unit is configured to obtain, e.g. receive, aninter prediction parameter and to perform inter prediction based on orusing the inter prediction parameter to obtain an inter prediction block265. Motion compensation, performed by the motion compensation unit, mayinvolve fetching or generating the prediction block based on themotion/block vector determined by motion estimation, possibly performinginterpolations to sub-pixel precision. Interpolation filtering maygenerate additional pixel samples from known pixel samples, thuspotentially increasing the number of candidate prediction blocks thatmay be used to code a picture block. Upon receiving the motion vectorfor the PU of the current picture block, the motion compensation unitmay locate the prediction block to which the motion vector points in oneof the reference picture lists.

The motion compensation unit may also generate syntax elementsassociated with the blocks and video slices for use by video decoder 30in decoding the picture blocks of the video slice. In addition or as analternative to slices and respective syntax elements, tile groups and/ortiles and respective syntax elements may be generated or used.

Entropy Coding

The entropy encoding unit 270 is configured to apply, for example, anentropy encoding algorithm or scheme (e.g. a variable length coding(VLC) scheme, an context adaptive VLC scheme (CAVLC), an arithmeticcoding scheme, a binarization, a context adaptive binary arithmeticcoding (CABAC), syntax-based context-adaptive binary arithmetic coding(SBAC), probability interval partitioning entropy (PIPE) coding oranother entropy encoding methodology or technique) or bypass (nocompression) on the quantized coefficients 209, inter predictionparameters, intra prediction parameters, loop filter parameters and/orother syntax elements to obtain encoded picture data 21 which can beoutput via the output 272, e.g. in the form of an encoded bitstream 21,so that, e.g., the video decoder 30 may receive and use the parametersfor decoding, The encoded bitstream 21 may be transmitted to videodecoder 30, or stored in a memory for later transmission or retrieval byvideo decoder 30.

Other structural variations of the video encoder 20 can be used toencode the video stream. For example, anon-transform based encoder 20can quantize the residual signal directly without the transformprocessing unit 206 for certain blocks or frames. In anotherimplementation, an encoder 20 can have the quantization unit 208 and theinverse quantization unit 210 combined into a single unit.

Decoder and Decoding Method

FIG. 3 shows an example of a video decoder 30 that is configured toimplement the techniques of this present application. The video decoder30 is configured to receive encoded picture data 21 (e.g. encodedbitstream 21), e.g. encoded by encoder 20, to obtain a decoded picture331. The encoded picture data or bitstream comprises information fordecoding the encoded picture data, e.g. data that represents pictureblocks of an encoded video slice (and/or tile groups or tiles) andassociated syntax elements.

In the example of FIG. 3, the decoder 30 comprises an entropy decodingunit 304, an inverse quantization unit 310, an inverse transformprocessing unit 312, a reconstruction unit 314 (e.g. a summer 314), aloop filter 320, a decoded picture buffer (DBP) 330, a mode applicationunit 360, an inter prediction unit 344 and an intra prediction unit 354.Inter prediction unit 344 may be or include a motion compensation unit.Video decoder 30 may, in some examples, perform a decoding passgenerally reciprocal to the encoding pass described with respect tovideo encoder 100 from FIG. 2.

As explained with regard to the encoder 20, the inverse quantizationunit 210, the inverse transform processing unit 212, the reconstructionunit 214 the loop filter 220, the decoded picture buffer (DPB) 230, theinter prediction unit 344 and the intra prediction unit 354 are alsoreferred to as forming the “built-in decoder” of video encoder 20.Accordingly, the inverse quantization unit 310 may be identical infunction to the inverse quantization unit 110, the inverse transformprocessing unit 312 may be identical in function to the inversetransform processing unit 212, the reconstruction unit 314 may beidentical in function to reconstruction unit 214, the loop filter 320may be identical in function to the loop filter 220, and the decodedpicture buffer 330 may be identical in function to the decoded picturebuffer 230. Therefore, the explanations provided for the respectiveunits and functions of the video 20 encoder apply correspondingly to therespective units and functions of the video decoder 30.

Entropy Decoding

The entropy decoding unit 304 is configured to parse the bitstream 21(or in general encoded picture data 21) and perform, for example,entropy decoding to the encoded picture data 21 to obtain, e.g.,quantized coefficients 309 and/or decoded coding parameters (not shownin FIG. 3), e.g. any or all of inter prediction parameters (e.g.reference picture index and motion vector), intra prediction parameter(e.g. intra prediction mode or index), transform parameters,quantization parameters, loop filter parameters, and/or other syntaxelements. Entropy decoding unit 304 may be configured to apply thedecoding algorithms or schemes corresponding to the encoding schemes asdescribed with regard to the entropy encoding unit 270 of the encoder20. Entropy decoding unit 304 may be further configured to provide interprediction parameters, intra prediction parameter and/or other syntaxelements to the mode application unit 360 and other parameters to otherunits of the decoder 30. Video decoder 30 may receive the syntaxelements at the video slice level and/or the video block level. Inaddition or as an alternative to slices and respective syntax elements,tile groups and/or tiles and respective syntax elements may be receivedand/or used.

Inverse Quantization

The inverse quantization unit 310 may be configured to receivequantization parameters (QP) (or in general information related to theinverse quantization) and quantized coefficients from the encodedpicture data 21 (e.g. by parsing and/or decoding, e.g. by entropydecoding unit 304) and to apply based on the quantization parameters aninverse quantization on the decoded quantized coefficients 309 to obtaindequantized coefficients 311, which may also be referred to as transformcoefficients 311. The inverse quantization process may include use of aquantization parameter determined by video encoder 20 for each videoblock in the video slice (or tile or tile group) to determine a degreeof quantization and, likewise, a degree of inverse quantization thatshould be applied.

Inverse Transform

Inverse transform processing unit 312 may be configured to receivedequantized coefficients 311, also referred to as transform coefficients311, and to apply a transform to the dequantized coefficients 311 inorder to obtain reconstructed residual blocks 213 in the sample domain.The reconstructed residual blocks 213 may also be referred to astransform blocks 313. The transform may be an inverse transform, e.g.,an inverse DCT, an inverse DST, an inverse integer transform, or aconceptually similar inverse transform process. The inverse transformprocessing unit 312 may be further configured to receive transformparameters or corresponding information from the encoded picture data 21(e.g. by parsing and/or decoding, e.g. by entropy decoding unit 304) todetermine the transform to be applied to the dequantized coefficients311.

Reconstruction

The reconstruction unit 314 (e.g. adder or summer 314) may be configuredto add the reconstructed residual block 313, to the prediction block 365to obtain a reconstructed block 315 in the sample domain, e.g. by addingthe sample values of the reconstructed residual block 313 and the samplevalues of the prediction block 365.

Filtering

The loop filter unit 320 (either in the coding loop or after the codingloop) is configured to filter the reconstructed block 315 to obtain afiltered block 321, e.g. to smooth pixel transitions, or otherwiseimprove the video quality. The loop filter unit 320 may comprise one ormore loop filters such as a de-blocking filter, a sample-adaptive offset(SAO) filter or one or more other filters, e.g. a bilateral filter, anadaptive loop filter (ALF), a sharpening, a smoothing filters or acollaborative filters, or any combination thereof. Although the loopfilter unit 320 is shown in FIG. 3 as being an in loop filter, in otherconfigurations, the loop filter unit 320 may be implemented as a postloop filter.

Decoded Picture Buffer

The decoded video blocks 321 of a picture are then stored in decodedpicture buffer 330, which stores the decoded pictures 331 as referencepictures for subsequent motion compensation for other pictures and/orfor output respectively display.

The decoder 30 is configured to output the decoded picture 311, e.g. viaoutput 312, for presentation or viewing to a user.

Prediction

The inter prediction unit 344 may be identical to the inter predictionunit 244 (in particular to the motion compensation unit) and the intraprediction unit 354 may be identical to the inter prediction unit 254 infunction, and performs split or partitioning decisions and predictionbased on the partitioning and/or prediction parameters or respectiveinformation received from the encoded picture data 21 (e.g. by parsingand/or decoding, e.g. by entropy decoding unit 304). Mode applicationunit 360 may be configured to perform the prediction (intra or interprediction) per block based on reconstructed pictures, blocks orrespective samples (filtered or unfiltered) to obtain the predictionblock 365.

When the video slice is coded as an intra coded (I) slice, intraprediction unit 354 of mode application unit 360 is configured togenerate prediction block 365 for a picture block of the current videoslice based on a signaled intra prediction mode and data from previouslydecoded blocks of the current picture. When the video picture is codedas an inter coded (i.e., B, or P) slice, inter prediction unit 344 (e.g.motion compensation unit) of mode application unit 360 is configured toproduce prediction blocks 365 for a video block of the current videoslice based on the motion vectors and other syntax elements receivedfrom entropy decoding unit 304. For inter prediction, the predictionblocks may be produced from one of the reference pictures within one ofthe reference picture lists. Video decoder 30 may construct thereference frame lists, List 0 and List 1, using default constructiontechniques based on reference pictures stored in DPB 330. The same orsimilar may be applied for or by embodiments using tile groups (e.g.video tile groups) and/or tiles (e.g. video tiles) in addition oralternatively to slices (e.g. video slices), e.g. a video may be codedusing I, P or B tile groups and/or tiles.

Mode application unit 360 is configured to determine the predictioninformation for a video block of the current video slice by parsing themotion vectors or related information and other syntax elements, anduses the prediction information to produce the prediction blocks for thecurrent video block being decoded. For example, the mode applicationunit 360 uses some of the received syntax elements to determine aprediction mode (e.g., intra or inter prediction) used to code the videoblocks of the video slice, an inter prediction slice type (e.g., Bslice, P slice, or GPB slice), construction information for one or moreof the reference picture lists for the slice, motion vectors for eachinter encoded video block of the slice, inter prediction status for eachinter coded video block of the slice, and other information to decodethe video blocks in the current video slice. The same or similar may beapplied for or by embodiments using tile groups (e.g. video tile groups)and/or tiles (e.g. video tiles) in addition or alternatively to slices(e.g. video slices), e.g. a video may be coded using I, P or B tilegroups and/or tiles.

Embodiments of the video decoder 30 as shown in FIG. 3 may be configuredto partition and/or decode the picture by using slices (also referred toas video slices), wherein a picture may be partitioned into or decodedusing one or more slices (typically non-overlapping), and each slice maycomprise one or more blocks (e.g. CTUs).

Embodiments of the video decoder 30 as shown in FIG. 3 may be configuredto partition and/or decode the picture by using tile groups (alsoreferred to as video tile groups) and/or tiles (also referred to asvideo tiles), wherein a picture may be partitioned into or decoded usingone or more tile groups (typically non-overlapping), and each tile groupmay comprise, e.g. one or more blocks (e.g. CTUs) or one or more tiles,wherein each tile, e.g. may be of rectangular shape and may comprise oneor more blocks (e.g. CTUs), e.g. complete or fractional blocks.

Other variations of the video decoder 30 can be used to decode theencoded picture data 21. For example, the decoder 30 can produce theoutput video stream without the loop filtering unit 320. For example, anon-transform based decoder 30 can inverse-quantize the residual signaldirectly without the inverse-transform processing unit 312 for certainblocks or frames. In another implementation, the video decoder 30 canhave the inverse-quantization unit 310 and the inverse-transformprocessing unit 312 combined into a single unit.

It should be understood that, in the encoder 20 and the decoder 30, aprocessing result of a current step may be further processed and thenoutput to the next step. For example, after interpolation filtering,motion vector derivation or loop filtering, a further operation, such asClip or shift, may be performed on the processing result of theinterpolation filtering, motion vector derivation or loop filtering.

It should be noted that further operations may be applied to the derivedmotion vectors of current block (including but not limit to controlpoint motion vectors of affine mode, sub-block motion vectors in affine,planar, ATMVP modes, temporal motion vectors, and so on). For example,the value of motion vector is constrained to a predefined rangeaccording to its representing bit. If the representing bit of motionvector is bitDepth, then the range is −2{circumflex over( )}(bitDepth−1)˜2{circumflex over ( )}(bitDepth−1)−1, where“{circumflex over ( )}” means exponentiation. For example, if bitDepthis set equal to 16, the range is −32768˜32767; if bitDepth is set equalto 18, the range is −131072˜131071. For example, the value of thederived motion vector (e.g. the MVs of four 4×4 sub-blocks within one8×8 block) is constrained such that the max difference between integerparts of the four 4×4 sub-block MVs is no more than N pixels, such as nomore than 1 pixel. Here provides two methods for constraining the motionvector according to the bitDepth.

FIG. 4 is a schematic diagram of a video coding device 400 according toan embodiment of the disclosure. The video coding device 400 is suitablefor implementing the disclosed embodiments as described herein. In anembodiment, the video coding device 400 may be a decoder such as videodecoder 30 of FIG. 1A or an encoder such as video encoder 20 of FIG. 1A.

The video coding device 400 comprises ingress ports 410 (or input ports410) and receiver units (Rx) 420 for receiving data; a processor, logicunit, or central processing unit (CPU) 430 to process the data;transmitter units (Tx) 440 and egress ports 450 (or output ports 450)for transmitting the data; and a memory 460 for storing the data. Thevideo coding device 400 may also comprise optical-to-electrical (OE)components and electrical-to-optical (EO) components coupled to theingress ports 410, the receiver units 420, the transmitter units 440,and the egress ports 450 for egress or ingress of optical or electricalsignals.

The processor 430 is implemented by hardware and software. The processor430 may be implemented as one or more CPU chips, cores (e.g., as amulti-core processor), FPGAs, ASICs, and DSPs. The processor 430 is incommunication with the ingress ports 410, receiver units 420,transmitter units 440, egress ports 450, and memory 460. The processor430 comprises a coding module 470. The coding module 470 implements thedisclosed embodiments described above. For instance, the coding module470 implements, processes, prepares, or provides the various codingoperations. The inclusion of the coding module 470 therefore provides asubstantial improvement to the functionality of the video coding device400 and effects a transformation of the video coding device 400 to adifferent state. Alternatively, the coding module 470 is implemented asinstructions stored in the memory 460 and executed by the processor 430.

The memory 460 may comprise one or more disks, tape drives, andsolid-state drives and may be used as an over-flow data storage device,to store programs when such programs are selected for execution, and tostore instructions and data that are read during program execution. Thememory 460 may be, for example, volatile and/or non-volatile and may bea read-only memory (ROM), random access memory (RAM), ternarycontent-addressable memory (TCAM), and/or static random-access memory(SRAM).

FIG. 5 is a simplified block diagram of an apparatus 500 that may beused as either or both of the source device 12 and the destinationdevice 14 from FIG. 1 according to an exemplary embodiment.

A processor 502 in the apparatus 500 can be a central processing unit.Alternatively, the processor 502 can be any other type of device, ormultiple devices, capable of manipulating or processing informationnow-existing or hereafter developed. Although the disclosedimplementations can be practiced with a single processor as shown, e.g.,the processor 502, advantages in speed and efficiency can be achievedusing more than one processor.

A memory 504 in the apparatus 500 can be a read only memory (ROM) deviceor a random access memory (RAM) device in an implementation. Any othersuitable type of storage device can be used as the memory 504. Thememory 504 can include code and data 506 that is accessed by theprocessor 502 using a bus 512. The memory 504 can further include anoperating system 508 and application programs 510, the applicationprograms 510 including at least one program that permits the processor502 to perform the methods described here. For example, the applicationprograms 510 can include applications 1 through N, which further includea video coding application that performs the methods described here.

The apparatus 500 can also include one or more output devices, such as adisplay 518. The display 518 may be, in one example, a touch sensitivedisplay that combines a display with a touch sensitive element that isoperable to sense touch inputs. The display 518 can be coupled to theprocessor 502 via the bus 512.

Although depicted here as a single bus, the bus 512 of the apparatus 500can be composed of multiple buses. Further, the secondary storage 514can be directly coupled to the other components of the apparatus 500 orcan be accessed via a network and can comprise a single integrated unitsuch as a memory card or multiple units such as multiple memory cards.The apparatus 500 can thus be implemented in a wide variety ofconfigurations.

The Intra Sub-Partition (ISP) coding tool partitions an intra(prediction) block into multiple sub-partitions, and predicts thesesub-partitions, for example, predicts one sub-partition at first andthen predicts a following sub-partition. In some situations, there mightbe discontinuities across the sub-partition boundaries causing blockartifacts.

In one example, FIG. 6 shows ISP partitioning of an intra block 600 intomultiple sub-partitions. In this example, there are two directionalpartitions, horizontal partition 601 and vertical partition 602; inother examples (not showed in FIG. 6), other partition such as anangular directional partition is performed. In the example shown in FIG.6, the sub-partitions and the corresponding boundaries with the verticalpartition 602 are labeled. Herein, the intra block 600 is divided intofour sub-partitions, namely, sub0, sub1, sub2, and sub3. Threesub-partition boundaries are labeled, namely, sub-partition boundary Abetween sub-partition 0 and 1, sub-partition boundary B betweensub-partition 1 and 2, sub-partition boundary C between sub-partition 2and 3, a similar definition may be used in the example of horizontalpartition 601.

In one embodiment, the prediction of sub-partitions is effected by theISP tool, the sub-partitions may be decoded sequentially. For onesub-partition, a residual signal may be generated by entropy decodingthe coefficients sent by the encoder and then inverse quantizing andinverse transforming them. Then, the sub-partition is intra predictedand finally the corresponding reconstructed samples are obtained byadding the residual signal to a prediction signal. The prediction signalmay basically represent the intra prediction which is done based on theangular mode from the top and left reference sample lines. Residual isdecoded and then added to the prediction signal to form the finalprediction These reconstructed samples are then used to predict the nextsub-partition. Therefore, the reconstructed values of one sub-partitionwill be available to generate the prediction of the next one, which willrepeat the process and so on. All sub-partitions (sub0, sub1, sub2,sub3) share the same intra mode.

Generally, two processing orders may be used for sub-partitions, normalorder and reverse order. In an example, for horizontal partition, normalorder is from top to bottom, reverse order is from bottom to top. Inanother example, for vertical partitions, normal order is from left toright, reverse order is from right to left.

As shown in FIG. 7, in order to reduce the block artifacts caused by theISP coding tool, sub-partition boundaries inside a block applied withISP are deblocking filtered after horizontal partitioning of a codingblock 700 into sub-partitions 701 or after vertical partitioning of acoding block 700 into sub-partitions 702. Several alternative methodsare proposed to apply deblocking filters on these sub-partitionboundaries.

Deblocking Filtering with Increased Boundary Strength.

Boundary strength (Bs) is a parameter that is used to control theintensity of deblocking filter. With a higher value of Bs, more samplesperpendicular to a boundary can be filtered. The prediction of ISP mightresults in a problem of error propagation, namely, the prediction erroris propagated with the processing order.

In one example as shown in FIG. 6, with vertical partition and normalprocessing order of a coding block (coding unit), samples in thesesub-partitions are reconstructed from left to right, namely, sub0, sub1,sub2, and sub3. Sub-partition 0 in general might have better predictionquality, as its reference samples (from the left neighboring block andtop neighboring block) have been already reconstructed. However, theleft part of reference samples of sub-partition 1 is from reconstructedsub-partition 0, therefore, sub-partition 1's reference samples mightnot as accurate as sub-partition 0's, resulting in more residual signal.Similarly, the reference samples of sub-partition 2 is further inferiorto sub-partition 1's, and prediction error propagated with theprocessing order.

A method of increasing boundary strength with the processing order isproposed. Namely, when a boundary between two sub-partitions (forexample boundary A, B, C in FIG. 6) is closer to neighboring blocks,then the Bs for this boundary is set to a smaller value, since theboundary has less error. When a boundary is farther from neighboringblocks, then the Bs for this boundary is set to a higher value, as theboundary has more error because of error propagation.

In one example as shown in FIG. 6, with vertical partition and normal(from left to right) processing order is performed to the block, the Bsof sub-partition boundary A is set to 0, the Bs of sub-partitionboundary B is set to 1, the Bs of sub-partition boundary C is set to 2.

In one example as shown in FIG. 6, with vertical partition and reverse(from right to left) processing order is performed to the block, the Bsof sub-partition boundary A is set to 2, the Bs of sub-partitionboundary B is set to 1, the Bs of sub-partition boundary C is set to 0.

In other examples, a similar process is performed for horizontalpartitions.

Deblocking Filtering Based on the Coded Block Flag (CBF).

In an example, each sub-partition is predicted and reconstructedseparately, each sub-partition might have different residual (thedifference between the original signal and predicted signal)information. In particular, a coded block flag (CBF) is used to indicatewhether a block or a sub-partition has residual data or not afterquantization. In general, a block with CBF equals to 1 (i.e. there isresidual data after quantization) has more distortion than a block withCBF equals to 0 (i.e. there is no residual data after quantization).This embodiment applies deblocking filter on a boundary between twosub-partitions based on the CBF flag of its two neighboringsub-partitions.

In one example, if each of the two sub-partitions of a sub-partitionboundary has a CBF flag value equals to 0, then no deblocking filter isapplied, otherwise (if at least one of the two sub-partitions of asub-partition boundary has a CBF flag value equals to 1) deblockingfilter is applied, the Bs value of the sub-partition boundary is setto 1. Raising an example in FIG. 6, if each of the sub-partition 0 and 1has a CBF flag equals to 0, then no deblocking filter is applied for thesub-partition boundary A. If at least sub-partition 0 and 1 has a CBFflag equals to 1, then deblocking filter is applied for thesub-partition boundary A, with Bs set to 1.

In one example, if each of the two sub-partitions of a sub-partitionboundary has a CBF flag value equals to 0, then no deblocking filter isapplied, otherwise (if at least one of the two sub-partitions of asub-partition boundary has a CBF flag value equals to 1) deblockingfilter is applied, with the Bs value of the sub-partition boundary isset to 2. Raising an example in FIG. 6, if each of sub-partition 0 and 1has a CBF flag equals to 0, then no deblocking filter is applied for thesub-partition A. If at least sub-partition 0 and 1 has a CBF flag equalsto 1, then deblocking filter is applied for the sub-partition boundaryA, with Bs set to 2.

Constant Boundary Strength Setting for Sub-Partition Boundaries.

In one example, for all sub-partition boundaries A, B, and C showed inFIG. 6, a constant Boundary strength (Bs) is set to 1.

In another example, for all sub-partition boundaries A, B, and C showedin FIG. 6, a constant Boundary strength (Bs) is set to 2.

As shown in FIG. 8, according to another example, after horizontalpartitioning of a coding block 800 into sub-partitions 801 or aftervertical partitioning of a coding block 800 into sub-partitions 802,only sub-partition boundaries which overlap with an 8×8 sample grid aredeblocked and the rest of the sub-partition edges are not deblocked.This has the advantage of reduced computational complexity as only a fewof the edges are deblocked.

Another alternative is shown in FIG. 9. In this case, after horizontalpartitioning of a coding block 900 into sub-partitions 901 or aftervertical partitioning of a coding block 900 into sub-partitions 902, allsub-partition boundaries which overlap with a 4×4 sample grid aredeblocked.

A coordinator of a position is defined as (x, y), x represents how manysamples away from the top-left sample of the whole frame in thehorizontal direction; y represents how many samples away from thetop-left sample of the whole frame in the vertical direction. Thecoordinator of the top-left sample of the whole frame is (0, 0).

In one example, an 8×8 sample grid can start from a position of (x, y),where x %8==0. The operation % means modular operation, defined as theremainder of x divided by 8.

In one example, an 8×8 sample grid can start from a position of (x, y),where x %8==4. The operation % means modular operation, defined as theremainder of x divided by 8.

In one example, an 8×8 sample grid can start from a position of (x, y),where y %8==0. The operation % means modular operation, defined as theremainder of y divided by 8.

In one example, an 8×8 sample grid can start from a position of (x, y),where y %8==4. The operation % means modular operation, defined as theremainder of y divided by 8.

Dealing with Smaller Blocks

Application of ISP may result in sub-partitions with height or width of4 samples. In the example shown in FIG. 6 using the vertical partition,if the W is 16 samples, then each sub-partition is 4 samples wide. Inthis case, as shown in FIG. 10, a weak filter that only modifies up toone sample 10314 or 10331 along the sub-partition boundaries 1032between the sub-partition 1031 and the sub-partition 33 can be used. Inthe example shown in FIG. 10, filtering is performed in each row of thesub-partitions 1031, 1033 that is perpendicular to and adjacent to thesub-partitions boundary 1032 between the sub-partition 1031 and thesub-partition 1033, for example. As shown in FIG. 10, a weak filter thatonly modifies up to one sample 1108 or 10311 along the edge 1020 betweenthe neighboring block 1010 and the current block 1030 can be used. Inanother example shown in FIG. 10, filtering is performed in each row ofthe sub-partition 1031 or the neighboring block 1010 that isperpendicular to and adjacent to the edge 1020 between the neighboringblock 1010 and the sub-partition 1031 of the block 1030, for example.Otherwise (if the sub-partition height/width orthogonal to sub-partitionboundaries is larger than 4 samples, then the normal VVC NET-L1001version 13 (http://phenix.it-sudparis.eu/jvet/doc end user/currentdocument. php?id=4834) deblocking filter (for example, a deblockingfilter disclosed in the above VVC document) may be used.

In another embodiment, for any one of above embodiments and examples,when sub-partition boundaries are not aligned with an 8×8 grid, thendeblocking filter is not applied.

The details of the Intra sub-partition related definition of theproposed method are described as follows in the format of thespecification of the VVC draft (part 7.3.9.5 and 7.4.10.5):

7.3.9.5 Coding Unit Syntax

... intra_subpartitions_mode_flag[ x0 ][ y0 ] ae(v) if(intra_subpartitions_mode_flag[ x0 ][ y0 ] == 1 )intra_subpartitions_split_flag[ x0 ][ y0 ] ae(v) ...

7.4.10.5 Coding Unit Semantics intra_subpartitions_mode_flag[ x0][y0]equal to 1 specifies that the current intra coding unit is partitionedinto NumIntraSubPartitions[x0][y0] rectangular transform blocksubpartitions. intra_subpartitions_mode_flag[x0][y0] equal to 0specifies that the current intra coding unit is not partitioned intorectangular transform block subpartitions. Whenintra_subpartitions_mode_flag[x0][y0] is not present, it is inferred tobe equal to 0. intra_subpartitions_split_flag[x0][y0] specifies whetherthe intra subpartitions split type is horizontal or vertical. Whenintra_subpartitions_split_flag[x0][y0] is not present, it is inferred asfollows:

-   -   If cbHeight is greater than MaxTbSizeY,        intra_subpartitions_split_flag[x0][y0] is inferred to be equal        to 0.    -   Otherwise (cbWidth is greater than MaxTbSizeY),        intra_subpartitions_split_flag[x0][y0] is inferred to be equal        to 1.

The variable IntraSubPartitionsSplitType specifies the type of splitused for the current luma coding block as illustrated in Table 13.IntraSubPartitionsSplitType is derived as follows:

-   -   If intra_subpartitions_mode_flag[x0][y0] is equal to 0,        IntraSubPartitionsSplitType is set equal to 0.    -   Otherwise, the IntraSubPartitionsSplitType is set equal to        1+intra_subpartitions_split_flag[x0][y0].

TABLE 13 Name association to IntraSubPartitionsSplitTypeIntraSubPartitionsSplitType Name of IntraSubPartitionsSplitType 0ISP_NO_SPLIT 1 ISP_HOR_SPLIT 2 ISP_VER_SPLIT

The variable NumIntraSubPartitions specifies the number of transformblock subpartitions into which an intra luma coding block is divided.NumIntraSubPartitions is derived as follows:

-   -   If IntraSubPartitionsSplitType is equal to ISP_NO_SPLIT,        NumIntraSubPartitions is set equal to 1.    -   Otherwise, if one of the following conditions is true,        NumIntraSubPartitions is set equal to 2:        -   cbWidth is equal to 4 and cbHeight is equal to 8,        -   cbWidth is equal to 8 and cbHeight is equal to 4.    -   Otherwise, NumIntraSubPartitions is set equal to 4.

FIG. 11 is a flowchart of a deblocking method, for deblockingsub-partitions boundary within a coding block in an image encodingand/or an image decoding, wherein the current coding block is coded inintra prediction mode and the current coding block is partitioned intosub-partitions comprising a first sub-partition and a secondsub-partition which is adjacent to the first sub-partition, wherein thesecond sub-partition is intra predicted based on the firstsub-partition. Further details of the method will be described above,e.g., with respect to FIGS. 6 to 10.

At step 1101, determining a first maximum filter length to be 1 for thefirst sub-partition and/or a second maximum filter length to be 1 forthe second sub-partition when a width of the first sub-partition is 4samples or a width of the second sub-partition is 4 samples, or when aheight of the first sub-partition is 4 samples or a height of the secondsub-partition is 4 samples;

At step 1103, modifying a value of up to one sample of the firstsub-partition, wherein the up to one sample is obtained from a row orcolumn of the first sub-partition that is perpendicular to and adjacentto the sub-partitions boundary between the first sub-partition and thesecond sub-partition; and/or

At step 1105, modifying a value of up to one sample of the secondsub-partition, wherein the up to one sample is obtained from a row orcolumn of the second sub-partition that is perpendicular to and adjacentto the sub-partitions boundary between the first sub-partition and thesecond sub-partition.

Based on the above, the present disclosure allows for modifying a smallnumber of sample values at the sub-partition boundary, and therefore themethod can reduce the blocking artifact that might be caused bysub-partition boundaries in a block applied with ISP, thus it improvesthe coding efficiency.

FIG. 12 is a flowchart of a deblocking method, for deblocking blockedges between image blocks in an image encoding and/or an imagedecoding, wherein the block edges comprise an edge between a currentsub-partition of a current coding block and a neighboring block of thecurrent coding block, wherein the current coding block is coded in intraprediction mode and the current coding block is partitioned intosub-partitions; Further details of the method will be described above,e.g., with respect to FIGS. 6 to 10.

At step 1201, determining a third maximum filter length to be 1 for thecurrent sub-partition and/or a fourth maximum filter length to be 1 forthe neighboring block when a width of the current sub-partition is 4samples or a height of the current sub-partition is 4 samples;

At step 1202, modifying a value of up to one sample of the currentsub-partition, wherein the up to one sample is obtained from a row orcolumn of the current sub-partition that is perpendicular to andadjacent to the edge between the current sub-partition and theneighboring block; and/or

At step 1203, modifying a value of up to one sample of the neighboringblock, wherein the up to one sample is obtained from a row or column ofthe neighboring block that is perpendicular to and adjacent to the edgebetween the current sub-partition and the neighboring block.

Based on the above, the present disclosure allows for modifying a smallnumber of sample values at the sub-partition boundary, and therefore themethod can reduce the blocking artifact that might be caused bysub-partition boundaries in a block applied with ISP while avoidingfiltering overlaps between a block edge and a sub-partition boundary toa certain extent, thus it improves the coding efficiency.

FIG. 13 is a block diagram illustrating an exemplary device 1300 forde-blocking sub-partitions boundary within a coding block according tothe techniques described in this disclosure (further details will bedescribed below, e.g., based on FIGS. 2 and 3 and FIGS. 6 to 10). Thedevice for use in an image encoder and/or an image decoder, fordeblocking sub-partitions boundary within a coding block, wherein thecurrent coding block is coded in intra prediction mode and the currentcoding block is partitioned into sub-partitions comprising a firstsub-partition and a second sub-partition which is adjacent to the firstsub-partition, in an example, the second sub-partition is intrapredicted based on the first sub-partition; wherein the device 1300comprises a de-blocking filter 1310 configured to:

determine a first maximum filter length to be 1 for the firstsub-partition and/or a second maximum filter length to be 1 for thesecond sub-partition when a width of the first sub-partition is 4samples or a width of the second sub-partition is 4 samples, or when aheight of the first sub-partition is 4 samples or a height of the secondsub-partition is 4 samples;

modify a value of up to one sample of the first sub-partition, whereinthe up to one sample is obtained from a row or column of the firstsub-partition that is perpendicular to and adjacent to thesub-partitions boundary between the first sub-partition and the secondsub-partition; and/or

modify a value of up to one sample of the second sub-partition, whereinthe up to one sample is obtained from a row or column of the secondsub-partition that is perpendicular to and adjacent to thesub-partitions boundary between the first sub-partition and the secondsub-partition.

FIG. 14 is a block diagram illustrating an exemplary device 1400 forde-blocking block edges according to the techniques described in thisdisclosure (further details will be described below, e.g., based onFIGS. 2 and 3 and FIGS. 6 to 10). The device for use in an image encoderand/or an image decoder, wherein the block edges comprises an edgebetween a current sub-partition of a current coding block and aneighboring block of the current coding block, wherein the currentcoding block is coded in intra prediction mode and the current codingblock is partitioned into sub-partitions;

wherein the device 1400 comprises a de-blocking filter 1410 configuredto:

determine a third maximum filter length to be 1 for the currentsub-partition and/or a fourth maximum filter length to be 1 for theneighboring block when a width of the current sub-partition is 4 samplesor a height of the current sub-partition is 4 samples;

modify a value of up to one sample of the current sub-partition, whereinthe up to one sample is obtained from a row or column of the currentsub-partition that is perpendicular to and adjacent to the edge betweenthe current sub-partition and the neighboring block; and/or

modify a value of up to one sample of the neighboring block, wherein theup to one sample is obtained from a row or column of the neighboringblock that is perpendicular to and adjacent to the edge between thecurrent sub-partition and the neighboring block.

FIG. 15 is a flowchart of a method of coding implemented in a decodingdevice or an encoding device.

At step 1501, generating a reconstructed block of a current coding blockwhich belongs to a current picture, wherein the current coding block iscoded in intra prediction mode and the current coding block ispartitioned into sub-partitions comprising a first sub-partition and asecond sub-partition, wherein the second sub-partition is intrapredicted based on the first sub-partition; and

At step 1502, performing filtering on a reconstructed picture of thecurrent picture, wherein the performing filtering on the reconstructedpicture of the current picture comprises: filtering up to one sample ina current sub-partition of reconstructed sub-partitions of thereconstructed block when a height of the current sub-partition is 4samples or when a width of the current sub-partition is 4 samples,wherein the one sample is positioned in a row or column of the currentsub-partition perpendicular to a boundary between the currentsub-partition and another sub-partition that is positioned adjacent tothe current sub-partition and the one sample is adjacent to theboundary.

In some implementation form of the embodiment, wherein a value of theone sample, which is obtained from the column of the currentsub-partition that is perpendicular to and adjacent to the boundarybetween the current sub-partition and said another sub-partition that isbelow or top of the current sub-partition, is modified when a height ofthe current sub-partition is 4 samples if an intra sub-partitions splittype of partitioning the current coding block into sub-partitions ishorizontal.

In some implementation form of the embodiment, wherein the value of theone sample, which is obtained from the row of the current sub-partitionthat is perpendicular to and adjacent to the boundary between thecurrent sub-partition and said another sub-partition that is left orright to the current sub-partition, is modified when a width of thecurrent sub-partition is 4 samples if an intra sub-partitions split typeof partitioning the current coding block into sub-partitions isvertical.

In some implementation form of the embodiment, wherein if the intrasub-partitions split type of partitioning the current coding block intosub-partitions is horizontal, the boundary between the currentsub-partition and said another sub-partition that is positioned adjacentto the current sub-partition is a horizontal sub-partitions boundary; orif the intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is vertical, the boundary between thecurrent sub-partition and said another sub-partition that is positionedadjacent to the current sub-partition is a vertical sub-partitionsboundary.

In some implementation form of the embodiment, wherein if the intrasub-partitions split type of partitioning the current coding block intosub-partitions is vertical, the first sub-partition is left to thesecond sub-partition and the second sub-partition is intra predictedbased on a reconstructed value of the first sub-partition;

if the intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is horizontal, the first sub-partitionis atop of the second sub-partition and the second sub-partition isintra predicted based on a reconstructed value of the firstsub-partition.

In some implementation form of the embodiment, wherein the currentsub-partition is a reconstructed version of the first sub-partition or areconstructed version of the second sub-partition.

In some implementation form of the embodiment, wherein the number ofsub-partitions is 2 or 4.

In some implementation form of the embodiment, wherein

if a width of the coding block is equal to 4 and a height of the codingblock is equal to 8 and/or if the width of the coding block is equal to8 and the height of the coding block is equal to 4, the number ofsub-partitions is 2,

Otherwise, the number of sub-partitions is 4.

In a further possible implementation form of the embodiment, wherein thefiltering of the up to one sample in the current sub-partition isperformed only if the boundary between the current sub-partition and theother sub-partition overlaps with an n×n sample grid of thereconstructed block wherein n is an integer. For example, n=4 or n=8.Thereby, the computational load may be even further reduced.

In a further possible implementation form of the embodiment, wherein thefiltering of up to one sample in the current sub-partition is performedonly when the heights of all of the sub-partitions are 4 samples or whenthe widths of all of the sub-partitions are 4 samples. Thereby, thecomputational load of the overall coding process may be further reduced.

In particular, wherein the sub-partitions are rectangular transformblock sub-partitions. When ISP is divided, each sub-partition is atransform block.

In the present disclosure, wherein the coding block is coded using anIntra sub-partition, ISP, tool.

In a further possible implementation form of the embodiment, wherein theorder of intra predicting the sub-partitions is from left to right orfrom right to left if the intra subpartitions split type of partitioningthe current coding block into sub-partitions is vertical (e.g. thepartitioning of the prediction block into the sub-partitions may beperformed in a vertical direction), or

wherein the order of intra predicting the at sub-partitions is from topto down or from down to top if the intra subpartitions split type ofpartitioning the current coding block into sub-partitions is horizontal(the partitioning of the prediction block into the sub-partitions may beperformed in a horizontal direction).

In particular, the current sub-partition is a reconstructed version(i.e. reconstructed values) of the first sub-partition or areconstructed version (i.e. reconstructed values) of the secondsub-partition. The number of sub-partitions can be 2 or 4, for example.

The coding block may be coded using an Intra sub-partition, ISP, tool.The ISP coding tool only applies to the coding block with intraprediction. The partitioning of the coding block/intra prediction blockmay result in 1D sub-partitions or a line of sub-partitions. If themethod is for use in an image encoding, the generation of thereconstructed block is based on the following process flow (as it isknown in the art): calculation of a residual block based on a currentblock (i.e. an original block) and the intra prediction block, transformand quantization of the residual coefficients of the residual block,inverse quantization and inverse transform in order to obtain areconstructed residual block (see also detailed description below). Thereconstructed block is obtained based on the reconstructed residualblock and the prediction block. If the method is for use in an imagedecoding, the generation of the reconstructed block is based on thefollowing process flow (as it is known in the art): obtaining residualcoefficients of a residual block based on information included in thereceived bitstream, transform and quantization of the residualcoefficients of the residual block, inverse quantization and inversetransform in order to obtain a reconstructed residual block (see alsodetailed description below). The reconstructed block is obtained basedon the reconstructed residual block and the prediction block.Furthermore, the reconstructed picture of a current image comprising thecurrent block is input into a filtering process, in block-based imagecoding scheme, by filtering up to one sample a filtering of a boundarycomprising modifying up to one sample adjacent to the block boundary ismeant. Decision of this kind of deblocking may be based on only threesamples (neighbored in the same row for filtering of boundaries betweenvertical sub-partitions or neighbored in the same column for filteringof boundaries between horizontal sub-partitions; see also detaileddescription above).

In general, boundary strengths of all boundaries between thesub-partitions of the coding block may be set to a constant valueindicating the strength of the filtering process (for example, 2) inorder to simplify the overall processing.

The weak filtering employed according to embodiments of the invention(up to one sample) allows for reducing block artifacts in small blockswithout the need for an unnecessary high computational load and memoryresources.

FIG. 16 is a flowchart of another method of coding implemented in adecoding device or an encoding device.

At step 1601, generating a reconstructed block of a current coding blockwhich belongs to a current picture, wherein the current coding block iscoded in intra prediction mode and the current coding block ispartitioned into sub-partitions comprising a first sub-partition and asecond sub-partition, wherein the second sub-partition is intrapredicted based on the first sub-partition; and

At step 1603, performing filtering on a reconstructed picture of thecurrent picture, wherein the performing filtering on the reconstructedpicture of the current picture comprises: filtering a boundary between acurrent sub-partition of the reconstructed block and a neighboring blockwhich is adjacent to the current sub-partition (i.e. a neighboring blockof the current block), based on a maximum filter length of the currentsub-partition and a maximum filter length of the neighboring block, andthe maximum filter length of the current sub-partition and the maximumfilter length of the neighboring block being 1 when a height of thecurrent sub-partition is 4 samples or when a width of the currentsub-partition is 4 samples.

In an example, wherein the step 1203 may include:

modifying, based on the maximum filter length MA of the currentsub-partition, one sample value of the current sub-partition adjacent tothe boundary; and

modifying, based on the maximum filter length MB of the neighboringblock, sample values of the neighboring block adjacent to the boundary.

MA=1, MB=1.

In particular, the step 1203 may include:

modifying at most a number MA of sample value of the currentsub-partition and the at most a number MA of the sample is in a lineperpendicular to and adjacent to the boundary, MA=1; and

wherein the modifying, based on a maximum filter length MB, samplevalues of the neighboring block adjacent to the boundary, comprises:

modifying at most a number MB of sample values of the neighboring blockand the at most a number MB of the samples are in a line perpendicularto and adjacent to the boundary, MB=1.

Here, the maximum filter length of the current sub-partition refers tothe number of samples allowed to be modified in the filtering processfor the current sub-partition. The maximum filter length of theneighboring block refers to the number of samples allowed to be modifiedin the filtering process for the neighboring block.

In some implementation form of the embodiment, wherein the firstsub-partition is intra predicted based on another reconstructed blockthat is positioned adjacent to the coding block.

In a further possible implementation form of the embodiment, wherein thefiltering is performed only if the boundary overlaps with an n×n samplegrid of the reconstructed block wherein n is an integer. For example, nis 4 or 8.

In some implementation form of the embodiment, wherein the value of onesample, which is obtained from the column of the current sub-partitionthat is perpendicular to and adjacent to the boundary between thecurrent sub-partition and said neighboring block that is below or top ofthe current sub-partition, is modified when a height of the currentsub-partition is 4 samples if an intra sub-partitions split type ofpartitioning the current coding block into sub-partitions is horizontal.

In some implementation form of the embodiment, wherein the value of onesample, which is obtained from the row of the current sub-partition thatis perpendicular to and adjacent to the boundary between the currentsub-partition and said neighboring block that is left or right to thecurrent sub-partition, is modified when a width of the currentsub-partition is 4 samples if an intra sub-partitions split type ofpartitioning the current coding block into sub-partitions is vertical.

In some implementation form of the embodiment, wherein if the intrasub-partitions split type of partitioning the current coding block intosub-partitions is horizontal, the boundary between the currentsub-partition and said neighboring block that is positioned adjacent tothe current sub-partition is a horizontal boundary; or

if the intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is vertical, the boundary between thecurrent sub-partition and said neighboring block that is positionedadjacent to the current sub-partition is a vertical boundary.

In some implementation form of the embodiment, wherein if the intrasub-partitions split type of partitioning the current coding block intosub-partitions is vertical, the first sub-partition is left to thesecond sub-partition and the second sub-partition is intra predictedbased on a reconstructed value of the first sub-partition;

if the intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is horizontal, the first sub-partitionis top of the second sub-partition and the second sub-partition is intrapredicted based on a reconstructed value of the first sub-partition.

In particular, the number of sub-partitions is 2 or 4. When the numberof sub-partitions is 2, corresponding, there are the first sub-partitionand the second sub-partition inside the current block and the currentsub-partition may be a reconstructed version of the first sub-partitionor a reconstructed version of the second sub-partition.

When the number of sub-partitions is 4, corresponding, there are thefirst sub-partition, the second sub-partition, the third sub-partitionand the fourth sub-partition inside the current block and the currentsub-partition may be a reconstructed version of the first sub-partitionor a reconstructed version of the fourth sub-partition.

It can be understood that the first sub-partition, the secondsub-partition, the third sub-partition, and the fourth sub-partition aremerely used for differently the sub-partitions. In some cases, theheights of all of the sub-partitions are 4 samples or the widths of allof the sub-partitions are 4 samples.

In a further possible implementation form of the embodiment, wherein

if a width of the coding block is equal to 4 and a height of the codingblock is equal to 8 and/or if the width of the coding block is equal to8 and the height of the coding block is equal to 4, the number ofsub-partitions is 2,

Otherwise, the number of sub-partitions is 4.

In a further possible implementation form of the embodiment, wherein thefiltering is performed only if the boundary overlaps with an n×n samplegrid of the reconstructed block wherein n is an integer. For example, nis 4 or 8.

In particular, wherein the sub-partitions are rectangular transformblock sub-partitions.

In the present disclosure, wherein the coding block is coded using anIntra sub-partition, ISP, tool.

FIG. 17 is a block diagram illustrating an exemplary device 1700according to the techniques described in this disclosure (furtherdetails will be described below, e.g., based on FIGS. 6-10, and FIG.15). The device is intended for use in an image encoder and/or an imagedecoder. In an example, the device 1700 may be corresponding to theencoder in FIG. 2. In another example, the device 1700 may becorresponding to the decoder in FIG. 3. The device may include:

a reconstruction unit 1701 configured to generate a reconstructed blockof a current coding block which belongs to a current picture, whereinthe current coding block is coded in intra prediction mode and thecurrent coding block is partitioned into sub-partitions comprising afirst sub-partition and a second sub-partition, wherein the secondsub-partition is intra predicted based on the first sub-partition; anda filtering unit 1730 configured to perform filtering on a reconstructedpicture of the current picture, wherein the filtering unit 1730 isconfigured to filter up to one sample in a current sub-partition ofreconstructed sub-partitions of the reconstructed block when a height ofthe current sub-partition is 4 samples or when a width of the currentsub-partition is 4 samples, wherein the one sample is positioned in arow or column of the current sub-partition perpendicular to a boundarybetween the current sub-partition and another sub-partition that ispositioned adjacent to the current sub-partition and the one sample isadjacent to the boundary.

FIG. 18 is a block diagram illustrating an exemplary device 1800according to the techniques described in this disclosure (furtherdetails will be described below, e.g., based on FIGS. 6-10, and FIG.16). The device is intended for use in an image encoder and/or an imagedecoder. In an example, the device 1800 may be corresponding to theencoder in FIG. 2. In another example, the device 1800 may becorresponding to the decoder in FIG. 3. The device may include:

a reconstruction unit 1810 configured to generate a reconstructed blockof a current coding block which belongs to a current picture, whereinthe current coding block is coded in intra prediction mode and thecurrent coding block is partitioned into sub-partitions comprising afirst sub-partition and a second sub-partition, wherein the secondsub-partition is intra predicted based on the first sub-partition; anda filtering unit 1830 configured to perform filtering on a reconstructedpicture of the current picture, wherein the filtering unit 1830 isconfigured to filter a boundary between a current sub-partition of thereconstructed block and a neighboring block which is adjacent to thecurrent sub-partition, based on a maximum filter length of the currentsub-partition and a maximum filter length of the neighboring block, andthe respective maximum filter lengths of the current sub-partition andthe neighboring block being 1 when a height of the current sub-partitionis 4 samples or when a width of the current sub-partition is 4 samples.

Based on the above, the present disclosure allows for modifying a smallnumber of sample values at the sub-partition boundary, and therefore themethod can reduce the blocking artifact that might be caused bysub-partition boundaries in a block applied with ISP while avoidingfiltering overlaps between a block edge and a sub-partition boundary toa certain extent, thus it improves the coding efficiency.

Following is an explanation of the applications of the encoding methodas well as the decoding method as shown in the above-mentionedembodiments, and a system using them.

FIG. 19 is a block diagram showing a content supply system 3100 forrealizing content distribution service. This content supply system 3100includes capture device 3102, terminal device 3106, and optionallyincludes display 3126. The capture device 3102 communicates with theterminal device 3106 over communication link 3104. The communicationlink may include the communication channel 13 described above. Thecommunication link 3104 includes but not limited to WIFI, Ethernet,Cable, wireless (3G/4G/5G), USB, or any kind of combination thereof, orthe like.

The capture device 3102 generates data, and may encode the data by theencoding method as shown in the above embodiments. Alternatively, thecapture device 3102 may distribute the data to a streaming server (notshown in the Figures), and the server encodes the data and transmits theencoded data to the terminal device 3106. The capture device 3102includes but not limited to camera, smart phone or Pad, computer orlaptop, video conference system, PDA, vehicle mounted device, or acombination of any of them, or the like. For example, the capture device3102 may include the source device 12 as described above. When the dataincludes video, the video encoder 20 included in the capture device 3102may actually perform video encoding processing. When the data includesaudio (i.e., voice), an audio encoder included in the capture device3102 may actually perform audio encoding processing. For some practicalscenarios, the capture device 3102 distributes the encoded video andaudio data by multiplexing them together. For other practical scenarios,for example in the video conference system, the encoded audio data andthe encoded video data are not multiplexed. Capture device 3102distributes the encoded audio data and the encoded video data to theterminal device 3106 separately.

In the content supply system 3100, the terminal device 310 receives andreproduces the encoded data. The terminal device 3106 could be a devicewith data receiving and recovering capability, such as smart phone orPad 3108, computer or laptop 3110, network video recorder (NVR)/digitalvideo recorder (DVR) 3112, TV 3114, set top box (STB) 3116, videoconference system 3118, video surveillance system 3120, personal digitalassistant (PDA) 3122, vehicle mounted device 3124, or a combination ofany of them, or the like capable of decoding the above-mentioned encodeddata. For example, the terminal device 3106 may include the destinationdevice 14 as described above. When the encoded data includes video, thevideo decoder 30 included in the terminal device is prioritized toperform video decoding. When the encoded data includes audio, an audiodecoder included in the terminal device is prioritized to perform audiodecoding processing.

For a terminal device with its display, for example, smart phone or Pad3108, computer or laptop 3110, network video recorder (NVR)/digitalvideo recorder (DVR) 3112, TV 3114, personal digital assistant (PDA)3122, or vehicle mounted device 3124, the terminal device can feed thedecoded data to its display. For a terminal device equipped with nodisplay, for example, STB 3116, video conference system 3118, or videosurveillance system 3120, an external display 3126 is contacted thereinto receive and show the decoded data.

When each device in this system performs encoding or decoding, thepicture encoding device or the picture decoding device, as shown in theabove-mentioned embodiments, can be used.

FIG. 20 is a diagram showing a structure of an example of the terminaldevice 3106. After the terminal device 3106 receives stream from thecapture device 3102, the protocol proceeding unit 3202 analyzes thetransmission protocol of the stream. The protocol includes but notlimited to Real Time Streaming Protocol (RTSP), Hyper Text TransferProtocol (HTTP), HTTP Live streaming protocol (HLS), MPEG-DASH,Real-time Transport protocol (RTP), Real Time Messaging Protocol (RTMP),or any kind of combination thereof, or the like.

After the protocol proceeding unit 3202 processes the stream, streamfile is generated. The file is outputted to a demultiplexing unit 3204.The demultiplexing unit 3204 can separate the multiplexed data into theencoded audio data and the encoded video data. As described above, forsome practical scenarios, for example in the video conference system,the encoded audio data and the encoded video data are not multiplexed.In this situation, the encoded data is transmitted to video decoder 3206and audio decoder 3208 without through the demultiplexing unit 3204.

Via the demultiplexing processing, video elementary stream (ES), audioES, and optionally subtitle are generated. The video decoder 3206, whichincludes the video decoder 30 as explained in the above mentionedembodiments, decodes the video ES by the decoding method as shown in theabove-mentioned embodiments to generate video frame, and feeds this datato the synchronous unit 3212. The audio decoder 3208, decodes the audioES to generate audio frame, and feeds this data to the synchronous unit3212. Alternatively, the video frame may store in a buffer (not shown inFIG. Y) before feeding it to the synchronous unit 3212. Similarly, theaudio frame may store in a buffer (not shown in FIG. Y) before feedingit to the synchronous unit 3212.

The synchronous unit 3212 synchronizes the video frame and the audioframe, and supplies the video/audio to a video/audio display 3214. Forexample, the synchronous unit 3212 synchronizes the presentation of thevideo and audio information. Information may code in the syntax usingtime stamps concerning the presentation of coded audio and visual dataand time stamps concerning the delivery of the data stream itself.

If subtitle is included in the stream, the subtitle decoder 3210 decodesthe subtitle, and synchronizes it with the video frame and the audioframe, and supplies the video/audio/subtitle to a video/audio/subtitledisplay 3216.

The present invention is not limited to the above-mentioned system, andeither the picture encoding device or the picture decoding device in theabove-mentioned embodiments can be incorporated into other system, forexample, a car system.

The invention has been described in conjunction with various embodimentsherein. However, other variations to the disclosed embodiments can beunderstood and effected by those skilled in the art in practicing theclaimed invention, from a study of the drawings, the disclosure and theappended claims. In the claims, the word “comprising” does not excludeother elements or steps and the indefinite article “a” or “an” does notexclude a plurality. A single processor or other unit may fulfill thefunctions of several items recited in the claims. The mere fact thatcertain measures are recited in usually different dependent claims doesnot indicate that a combination of these measures cannot be used toadvantage. A computer program may be stored/distributed on a suitablemedium, such as an optical storage medium or a solid-state mediumsupplied together with or as part of other hardware, but may also bedistributed in other forms, such as via the internet or other wired orwireless communication systems.

The person skilled in the art will understand that the “blocks”(“units”) of the various figures (method and apparatus) represent ordescribe functionalities of embodiments of the invention (rather thannecessarily individual “units” in hardware or software) and thusdescribe equally functions or features of apparatus embodiments as wellas method embodiments (unit=step).

The terminology of “units” is merely used for illustrative purposes ofthe functionality of embodiments of the encoder/decoder and are notintended to limiting the disclosure.

In the several embodiments provided in the present application, itshould be understood that the disclosed system, apparatus, and methodmay be implemented in other manners. For example, the describedapparatus embodiment is merely exemplary. For example, the unit divisionis merely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented by using some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected according toactual needs to achieve the objectives of the solutions of theembodiments.

In addition, functional units in the embodiments of the presentinvention may be integrated into one processing unit, or each of theunits may exist alone physically, or two or more units are integratedinto one unit.

Embodiments of the invention may further comprise an apparatus, e.g.encoder and/or decoder, which comprises a processing circuitryconfigured to perform any of the methods and/or processes describedherein.

Although embodiments of the invention have been primarily describedbased on video coding, it should be noted that embodiments of the codingsystem 10, encoder 20 and decoder 30 (and correspondingly the system 10)and the other embodiments described herein may also be configured forstill picture processing or coding, i.e. the processing or coding of anindividual picture independent of any preceding or consecutive pictureas in video coding. In general only inter-prediction units 244 (encoder)and 344 (decoder) may not be available in case the picture processingcoding is limited to a single picture 17. All other functionalities(also referred to as tools or technologies) of the video encoder 20 andvideo decoder 30 may equally be used for still picture processing, e.g.residual calculation 204/304, transform 206, quantization 208, inversequantization 210/310, (inverse) transform 212/312, partitioning 262/362,intra-prediction 254/354, and/or loop filtering 220, 320, and entropycoding 270 and entropy decoding 304.

Embodiments, e.g. of the encoder 20 and the decoder 30, and functionsdescribed herein, e.g. with reference to the encoder 20 and the decoder30, may be implemented in hardware, software, firmware, or anycombination thereof. If implemented in software, the functions may bestored on a computer-readable medium or transmitted over communicationmedia as one or more instructions or code and executed by ahardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limiting, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transitory media, but areinstead directed to non-transitory, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor,” as used herein may referto any of the foregoing structure or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated hardware and/or software modules configured for encoding anddecoding, or incorporated in a combined codec. Also, the techniquescould be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

1. A deblocking method, for deblocking a sub-partitions boundary withina coding block in image encoding or image decoding, wherein a currentcoding block is coded in an intra prediction mode and the current codingblock is partitioned into sub-partitions comprising a firstsub-partition and a second sub-partition which is adjacent to the firstsub-partition, the method comprising: determining one or more of a firstmaximum filter length to be 1 for the first sub-partition or a secondmaximum filter length to be 1 for the second sub-partition, when a widthof the first sub-partition is 4 samples or a width of the secondsub-partition is 4 samples, or when a height of the first sub-partitionis 4 samples or a height of the second sub-partition is 4 samples; andperforming one or more of: modifying, based at least in part upon thefirst maximum filter length, a value of up to one sample of the firstsub-partition, wherein the up to one sample is obtained from a row or acolumn of the first sub-partition that is perpendicular to and adjacentto the sub-partitions boundary between the first sub-partition and thesecond sub-partition; or modifying, based at least in part upon thesecond maximum filter length, a value of up to one sample of the secondsub-partition, wherein the up to one sample is obtained from a row or acolumn of the second sub-partition that is perpendicular to and adjacentto the sub-partitions boundary between the first sub-partition and thesecond sub-partition.
 2. The method according to claim 1, wherein the upto one sample, which is obtained from the column of the first or secondsub-partition that is perpendicular to and adjacent to thesub-partitions boundary between the first and second sub-partitions, ismodified when a height of the first or second sub-partition is 4samples, and if an intra sub-partitions split type of partitioning thecurrent coding block into sub-partitions is horizontal.
 3. The methodaccording to claim 1, wherein the up to one sample, which is obtainedfrom the row of the first or second sub-partition that is perpendicularto and adjacent to the sub-partitions boundary between the first andsecond sub-partitions, is modified when a width of the first or secondsub-partition is 4 samples, and if an intra sub-partitions split type ofpartitioning the current coding block into sub-partitions is vertical.4. The method according to claim 1, wherein, if an intra sub-partitionssplit type of partitioning the current coding block into sub-partitionsis horizontal, the sub-partitions boundary between the first and secondsub-partitions is a horizontal sub-partitions boundary; or if the intrasub-partitions split type of partitioning the current coding block intosub-partitions is vertical, the sub-partitions boundary between thefirst and second sub-partitions is a vertical sub-partitions boundary.5. The method according to claim 1, wherein, if an intra sub-partitionssplit type of partitioning the current coding block into sub-partitionsis vertical, the first sub-partition is located left of the secondsub-partition and the second sub-partition is intra predicted based on areconstructed value of the first sub-partition; and if the intrasub-partitions split type of partitioning the current coding block intosub-partitions is horizontal, the first sub-partition is located abovethe second sub-partition and the second sub-partition is intra predictedbased on a reconstructed value of the first sub-partition.
 6. The methodaccording to claim 1, wherein a number of sub-partitions in the currentcoding block is 2 or
 4. 7. The method according to claim 1, wherein if awidth of the current coding block is equal to 4 and a height of thecoding block is equal to 8 or if the width of the current coding blockis equal to 8 and the height of the current coding block is equal to 4,a number of sub-partitions in the current coding block is 2, otherwise,the number of sub-partitions is
 4. 8. The method according to claim 1,wherein the up to one sample in the first or second sub-partition ismodified even if the sub-partitions boundary between the first andsecond sub-partitions is not overlapped with an n×n sample grid, whereinn is an integer.
 9. The method according to claim 1, wherein the up toone sample in the first or second sub-partition is modified, only if thesub-partitions boundary between the first and second sub-partitionsoverlaps with an n× n sample grid, wherein n is an integer.
 10. Themethod according to claim 9, wherein n is 4 or
 8. 11. The methodaccording to claim 1, wherein samples of the sub-partitions are lumasamples, or the samples of the sub-partitions are chroma samples. 12.The method according to claim 1, wherein the sub-partitions arerectangular transform block sub-partitions.
 13. The method according toclaim 1, wherein an order of intra predicting the sub-partitions is fromleft to right, if an intra sub-partitions split type of partitioning thecurrent coding block into sub-partitions is vertical, or wherein theorder of intra predicting the sub-partitions is from top to bottom, ifthe intra sub-partitions split type of partitioning the current codingblock into sub-partitions is horizontal.
 14. The method according toclaim 1, wherein the current coding block is coded using an intrasub-partition (ISP) tool or the sub-partitions boundary is caused by anintra sub-partition (ISP) tool.
 15. A device for use in an image encoderor an image decoder, for deblocking sub-partitions boundary within acoding block, wherein a current coding block is coded in an intraprediction mode and the current coding block is partitioned intosub-partitions comprising a first sub-partition and a secondsub-partition which is adjacent to the first sub-partition; wherein thedevice comprises a de-blocking filter configured to: determine one ormore of a first maximum filter length to be 1 for the firstsub-partition or a second maximum filter length to be 1 for the secondsub-partition when a width of the first sub-partition is 4 samples or awidth of the second sub-partition is 4 samples, or when a height of thefirst sub-partition is 4 samples or a height of the second sub-partitionis 4 samples; and perform one or more of: modifying, based at least inpart upon the first maximum filter length, a value of up to one sampleof the first sub-partition, wherein the up to one sample is obtainedfrom a row or a column of the first sub-partition that is perpendicularto and adjacent to the sub-partitions boundary between the firstsub-partition and the second sub-partition; or modifying, based at leastin part upon the second maximum filter length, a value of up to onesample of the second sub-partition, wherein the up to one sample isobtained from a row or a column of the second sub-partition that isperpendicular to and adjacent to the sub-partitions boundary between thefirst sub-partition and the second sub-partition.
 16. The deviceaccording to claim 15, wherein the up to one sample, which is obtainedfrom the column of the first or second sub-partition that isperpendicular to and adjacent to the sub-partitions boundary between thefirst and second sub-partitions, is modified when a height of the firstor second sub-partition is 4 samples, and if an intra sub-partitionssplit type of partitioning the current coding block into sub-partitionsis horizontal.
 17. The device according to claim 15, wherein the up toone sample, which is obtained from the row of the first or secondsub-partition that is perpendicular to and adjacent to thesub-partitions boundary between the first and second sub-partitions, ismodified when a width of the first or second sub-partition is 4 samples,and if an intra sub-partitions split type of partitioning the currentcoding block into sub-partitions is vertical.
 18. The device accordingto claim 15, wherein if an intra sub-partitions split type ofpartitioning the current coding block into sub-partitions is horizontal,the sub-partitions boundary between the first and second sub-partitionsis a horizontal sub-partitions boundary; or if the intra sub-partitionssplit type of partitioning the current coding block into sub-partitionsis vertical, the sub-partitions boundary between the first and secondsub-partitions is a vertical sub-partitions boundary.
 19. The deviceaccording to claim 15, wherein if an intra sub-partitions split type ofpartitioning the current coding block into sub-partitions is vertical,the first sub-partition is left to the second sub-partition and thesecond sub-partition is intra predicted based on a reconstructed valueof the first sub-partition; and if the intra sub-partitions split typeof partitioning the current coding block into sub-partitions ishorizontal, the first sub-partition is above the second sub-partitionand the second sub-partition is intra predicted based on a reconstructedvalue of the first sub-partition.
 20. The device according to claim 15,wherein a number of sub-partitions in the current coding block is 2 or4.
 21. The device according to claim 15, wherein if a width of thecurrent coding block is equal to 4 and a height of the coding block isequal to 8 or if the width of the current coding block is equal to 8 andthe height of the current coding block is equal to 4, a number ofsub-partitions in the current coding block is 2, otherwise, the numberof sub-partitions is
 4. 22. The device according to claim 15, whereinthe up to one sample in the first or second sub-partition is modifiedeven if the sub-partitions boundary between the first and secondsub-partitions is not overlapped with an n× n sample grid, wherein n isan integer.
 23. The device according to claim 15, wherein the up to onesample in the first or second sub-partition is modified only if thesub-partitions boundary between the first and second sub-partitionsoverlaps with an n× n sample grid, wherein n is an integer.
 24. Thedevice according to claim 15, wherein n is 4 or
 8. 25. The deviceaccording to claim 15, wherein samples of the sub-partitions are lumasamples, or the samples of the sub-partitions are chroma samples. 26.The device according to claim 15, wherein the sub-partitions arerectangular transform block sub-partitions.
 27. The device according toclaim 15, wherein an order of intra predicting the sub-partitions isfrom left to right if an intra sub-partitions split type of partitioningthe current coding block into sub-partitions is vertical, or wherein theorder of intra predicting the sub-partitions is from top to bottom, ifthe intra sub-partitions split type of partitioning the current codingblock into sub-partitions is horizontal.
 28. The device according toclaim 15, wherein the current coding block is coded using an intrasub-partition (ISP) tool or the sub-partitions boundary is caused by anintra sub-partition (ISP) tool.
 29. A non-transitory computer-readablemedium carrying a program code which, when executed by a computingdevice, causes the computing device to perform operations for deblockinga sub-partitions boundary within an current coding block in imageencoding or image decoding, wherein the current coding block is coded inan intra prediction mode and the current coding block is partitionedinto sub-partitions comprising a first sub-partition and a secondsub-partition which is adjacent to the first sub-partition; wherein theoperations comprise: determining one or more of a first maximum filterlength to be 1 for the first sub-partition or a second maximum filterlength to be 1 for the second sub-partition when a width of the firstsub-partition is 4 samples or a width of the second sub-partition is 4samples, or when a height of the first sub-partition is 4 samples or aheight of the second sub-partition is 4 samples; and performing one ormore of: modifying, based at least in part upon the first maximum filterlength, a value of up to one sample of the first sub-partition, whereinthe up to one sample is obtained from a row or a column of the firstsub-partition that is perpendicular to and adjacent to thesub-partitions boundary between the first sub-partition and the secondsub-partition; or modifying, based at least in part upon the secondmaximum filter length, a value of up to one sample of the secondsub-partition, wherein the up to one sample is obtained from a row or acolumn of the second sub-partition that is perpendicular to and adjacentto the sub-partitions boundary between the first sub-partition and thesecond sub-partition.
 30. A device, comprising: one or more processors;and a non-transitory computer-readable storage medium coupled to the oneor more processors and storing programming for execution by the one ormore processors, wherein the programming, when executed by theprocessors, configures the device to carry out operations for deblockinga sub-partitions boundary within an current coding block in imageencoding or image decoding, wherein the current coding block is coded inan intra prediction mode and the current coding block is partitionedinto sub-partitions comprising a first sub-partition and a secondsub-partition which is adjacent to the first sub-partition; wherein theoperations comprises: determining one or more of a first maximum filterlength to be 1 for the first sub-partition or a second maximum filterlength to be 1 for the second sub-partition, when a width of the firstsub-partition is 4 samples or a width of the second sub-partition is 4samples, or when a height of the first sub-partition is 4 samples or aheight of the second sub-partition is 4 samples; and performing one ormore of: modifying, based at least in part upon the first maximum filterlength, a value of up to one sample of the first sub-partition, whereinthe up to one sample is obtained from a row or a column of the firstsub-partition that is perpendicular to and adjacent to thesub-partitions boundary between the first sub-partition and the secondsub-partition; or modifying, based at least in part upon the secondmaximum filter length, a value of up to one sample of the secondsub-partition, wherein the up to one sample is obtained from a row or acolumn of the second sub-partition that is perpendicular to and adjacentto the sub-partitions boundary between the first sub-partition and thesecond sub-partition.